#include <algorithm>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdlib>
#include <iomanip>
#include <iostream>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>
using namespace std;
// ============ Big Integer Library ============
// Reference:
// - https://github.com/indy256/codelibrary/blob/main/cpp/numeric/bigint.cpp
// - https://github.com/ngthanhtrung23/ACM_Notebook_new/blob/master/Math/bigint.h
// - https://github.com/koosaga/olympiad/blob/master/Library/codes/math/bigint.cpp
//
// Tested:
// - https://judge.yosupo.jp/problem/addition_of_big_integers
// - https://judge.yosupo.jp/problem/multiplication_of_big_integers
//
const int BASE_DIGITS = 9;
const int BASE = 1000000000;
struct BigInt {
int sign;
vector<int> a;
// ============ Constructors ============
// Default constructor
BigInt(void) : sign(1) {}
// 64-bit integer constructor
BigInt(long long v) { *this = v; }
BigInt& operator=(long long v) {
this->sign = v < 0 ? -1 : 1;
v *= this->sign;
this->a.clear();
for (; v > 0; v /= BASE) this->a.push_back(v % BASE);
return *this;
}
// String constructor
BigInt(const string &s) { read(s); }
// ============ Input/Output ============
void read(const string &s) {
this->sign = 1;
this->a.clear();
int pos = 0;
while (pos < static_cast<int>(s.length()) && (s[pos] == '-' || s[pos] == '+')) {
if (s[pos++] == '-') this->sign = -this->sign;
}
for (int i = static_cast<int>(s.length()) - 1; i >= pos; i -= BASE_DIGITS) {
int x = 0;
for (int j = max(pos, i - BASE_DIGITS + 1); j <= i; ++j) {
x = x * 10 + s[j] - '0';
}
this->a.push_back(x);
}
trim();
}
friend istream& operator>>(istream &in, BigInt &v) {
string s;
in >> s;
v.read(s);
return in;
}
friend ostream& operator<<(ostream &out, const BigInt &v) {
if (v.sign == -1 && !v.isZero()) out << '-';
out << (v.a.empty() ? 0 : v.a.back());
for (int i = static_cast<int>(v.a.size()) - 2; i >= 0; --i) {
out << setw(BASE_DIGITS) << setfill('0') << v.a[i];
}
return out;
}
// ============ Comparison ============
bool operator<(const BigInt &v) const {
if (this->sign != v.sign) return this->sign < v.sign;
if (this->a.size() != v.a.size()) return this->a.size() * this->sign < v.a.size() * v.sign;
for (int i = static_cast<int>(this->a.size()) - 1; i >= 0 ; --i) {
if (this->a[i] == v.a[i]) continue;
return this->a[i] * this->sign < v.a[i] * this->sign;
}
return false;
}
bool operator>(const BigInt &v) const { return v < *this; }
bool operator<=(const BigInt &v) const { return !(v < *this); }
bool operator>=(const BigInt &v) const { return !(*this < v); }
bool operator==(const BigInt &v) const { return !(*this < v) && !(v < *this); }
bool operator!=(const BigInt &v) const { return *this < v || v < *this; }
// Returns:
// -1 if |x| < |y|
// 0 if |x| == |y|
// 1 if |x| > |y|
friend int __compare_abs(const BigInt &x, const BigInt &y) {
if (x.a.size() != y.a.size()) return x.a.size() < y.a.size() ? -1 : 1;
for (int i = static_cast<int>(x.a.size()) - 1; i >= 0; --i) {
if (x.a[i] == y.a[i]) continue;
return x.a[i] < y.a[i] ? -1 : 1;
}
return 0;
}
// ============ Unary operators ============
BigInt operator+(void) const { return *this; }
BigInt operator-(void) const {
BigInt res = *this;
if (!res.isZero()) res.sign = -res.sign;
return res;
}
// ============ Addition ============
// NOTE: sign ignored
void __internal_add(const BigInt &v) {
if (this->a.size() < v.a.size()) this->a.resize(v.a.size(), 0);
for (int i = 0, carry = 0; i < static_cast<int>(this->a.size()) || i < static_cast<int>(v.a.size()) || carry; ++i) {
if (i == static_cast<int>(this->a.size())) this->a.push_back(0);
this->a[i] += carry + (i < static_cast<int>(v.a.size()) ? v.a[i] : 0);
carry = this->a[i] >= BASE;
if (carry) this->a[i] -= BASE;
}
}
BigInt operator+=(const BigInt &v) {
if (this->sign == v.sign) {
__internal_add(v);
} else if (__compare_abs(*this, v) >= 0) {
__internal_sub(v);
} else {
BigInt vv = v;
swap(*this, vv);
__internal_sub(vv);
}
return *this;
}
// Optimized operator+ for rvalue reference
// https://stackoverflow.com/questions/13166079/move-semantics-and-pass-by-rvalue-reference-in-overloaded-arithmetic
template <typename L, typename R> typename enable_if<is_convertible<L, BigInt>::value && is_convertible<R, BigInt>::value && is_lvalue_reference<R&&>::value, BigInt>::type friend operator+(L &&l, R &&r) {
BigInt result(std::forward<L>(l));
result += r;
return result;
}
// Optimized operator+ for lvalue reference
// https://stackoverflow.com/questions/13166079/move-semantics-and-pass-by-rvalue-reference-in-overloaded-arithmetic
template <typename L, typename R> typename enable_if<is_convertible<L, BigInt>::value && is_convertible<R, BigInt>::value && is_rvalue_reference<R&&>::value, BigInt>::type friend operator+(L &&l, R &&r) {
BigInt result(std::move(r));
result += l;
return result;
}
// ============ Subtraction ============
// NOTE: sign ignored
void __internal_sub(const BigInt &v) {
for (int i = 0, borrow = 0; i < static_cast<int>(v.a.size()) || borrow; ++i) {
this->a[i] -= borrow + (i < static_cast<int>(v.a.size()) ? v.a[i] : 0);
borrow = this->a[i] < 0;
if (borrow) this->a[i] += BASE;
}
this->trim();
}
BigInt operator-=(const BigInt &v) {
if (this->sign != v.sign) {
__internal_add(v);
} else if (__compare_abs(*this, v) >= 0) {
__internal_sub(v);
} else {
BigInt vv = v;
swap(*this, vv);
__internal_sub(vv);
this->sign = -this->sign;
}
return *this;
}
// Optimized operator- for rvalue reference
// https://stackoverflow.com/questions/13166079/move-semantics-and-pass-by-rvalue-reference-in-overloaded-arithmetic
template <typename L, typename R> typename enable_if<is_convertible<L, BigInt>::value && is_convertible<R, BigInt>::value, BigInt>::type friend operator-(L &&l, R &&r) {
BigInt result(std::forward<L>(l));
result -= r;
return result;
}
// ============ Multiplication ============
BigInt mul_simple(const BigInt &v) const {
BigInt res;
res.sign = this->sign * v.sign;
res.a.resize(this->a.size() + v.a.size());
for (int i = 0; i < static_cast<int>(this->a.size()); ++i) {
if (!this->a[i]) continue;
for (int j = 0, carry = 0; j < static_cast<int>(v.a.size()) || carry; ++j) {
long long cur = res.a[i + j] + static_cast<long long>(this->a[i]) * (j < static_cast<int>(v.a.size()) ? v.a[j] : 0) + carry;
carry = static_cast<int>(cur / BASE);
res.a[i + j] = static_cast<int>(cur % BASE);
}
}
res.trim();
return res;
}
void fft(vector<complex<double>> &a, bool inv) const {
int n = static_cast<int>(a.size()), j = 0;
vector<complex<double>> roots(n >> 1);
for (int i = 1; i < n; ++i) {
int bit = n >> 1;
for (; j >= bit; bit >>= 1) j -= bit;
j += bit;
if (i < j) swap(a[i], a[j]);
}
double ang = 2 * acos(double(-1)) / n * (inv ? -1 : 1);
for (int i = 0; i < n / 2; i++) roots[i] = complex<double>(cos(ang * i), sin(ang * i));
for (int i = 2; i <= n; i <<= 1) {
int step = n / i;
for (int j = 0; j < n; j += i) {
for (int k = 0; k < i / 2; ++k) {
complex<double> u = a[j + k], v = a[j + k + i / 2] * roots[step * k];
a[j + k] = u + v;
a[j + k + i / 2] = u - v;
}
}
}
if (inv) for (int i = 0; i < n; ++i) a[i] /= n;
}
void multiply_fft(const vector<int> &a, const vector<int> &b, vector<int> &res) const {
vector<complex<double>> fa(a.begin(), a.end());
vector<complex<double>> fb(b.begin(), b.end());
int n = 1;
while (n < static_cast<int>(max(a.size(), b.size()))) n <<= 1;
n <<= 1;
fa.resize(n);
fb.resize(n);
fft(fa, false);
fft(fb, false);
for (int i = 0; i < n; ++i) fa[i] *= fb[i];
fft(fa, true);
res.resize(n);
long long carry = 0;
for (int i = 0; i < n; ++i) {
long long t = static_cast<long long>(fa[i].real() + 0.5) + carry;
carry = t / 1000;
res[i] = t % 1000;
}
}
BigInt mul_fft(const BigInt &v) const {
BigInt res;
res.sign = this->sign * v.sign;
multiply_fft(convert_base(this->a, BASE_DIGITS, 3), convert_base(v.a, BASE_DIGITS, 3), res.a);
res.a = convert_base(res.a, 3, BASE_DIGITS);
res.trim();
return res;
}
// Convert BASE 10^from -> 10^to
static vector<int> convert_base(const vector<int> &a, int from, int to) {
vector<long long> p(max(from, to) + 1);
p[0] = 1;
for (int i = 1; i < static_cast<int>(p.size()); ++i) p[i] = p[i - 1] * 10;
vector<int> res;
long long cur = 0;
int cur_digits = 0;
for (int i = 0; i < static_cast<int>(a.size()); ++i) {
cur += a[i] * p[cur_digits];
cur_digits += from;
while (cur_digits >= to) {
res.push_back(static_cast<long long>(cur % p[to]));
cur /= p[to];
cur_digits -= to;
}
}
res.push_back(static_cast<int>(cur));
while (!res.empty() && !res.back()) res.pop_back();
return res;
}
static vector<long long> karatsubaMultiply(const vector<long long> &a, const vector<long long> &b) {
int n = static_cast<int>(a.size());
vector<long long> res(n + n);
if (n <= 32) {
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
res[i + j] += a[i] * b[j];
}
}
return res;
}
int k = n >> 1;
vector<long long> a1(a.begin(), a.begin() + k);
vector<long long> a2(a.begin() + k, a.end());
vector<long long> b1(b.begin(), b.begin() + k);
vector<long long> b2(b.begin() + k, b.end());
vector<long long> a1b1 = karatsubaMultiply(a1, b1);
vector<long long> a2b2 = karatsubaMultiply(a2, b2);
for (int i = 0; i < k; ++i) a2[i] += a1[i];
for (int i = 0; i < k; ++i) b2[i] += b1[i];
vector<long long> r = karatsubaMultiply(a2, b2);
for (int i = 0; i < static_cast<int>(a1b1.size()); ++i) r[i] -= a1b1[i];
for (int i = 0; i < static_cast<int>(a2b2.size()); ++i) r[i] -= a2b2[i];
for (int i = 0; i < static_cast<int>(r.size()); ++i) res[i + k] += r[i];
for (int i = 0; i < static_cast<int>(a1b1.size()); ++i) res[i] += a1b1[i];
for (int i = 0; i < static_cast<int>(a2b2.size()); ++i) res[i + n] += a2b2[i];
return res;
}
BigInt mul_karatsuba(const BigInt &v) const {
vector<int> a6 = convert_base(this->a, BASE_DIGITS, 6);
vector<int> b6 = convert_base(v.a, BASE_DIGITS, 6);
vector<long long> a(a6.begin(), a6.end());
vector<long long> b(b6.begin(), b6.end());
while (a.size() < b.size()) a.push_back(0);
while (b.size() < a.size()) b.push_back(0);
// TODO: What happens if a.size() == b.size() == 0? Is it possible?
while (a.size() & (a.size() - 1)) a.push_back(0), b.push_back(0);
vector<long long> c = karatsubaMultiply(a, b);
BigInt res;
res.sign = this->sign * v.sign;
long long carry = 0;
for (int i = 0; i < static_cast<int>(c.size()); ++i) {
long long cur = c[i] + carry;
res.a.push_back(static_cast<int>(cur % 1000000));
carry = cur / 1000000;
}
res.a = convert_base(res.a, 6, BASE_DIGITS);
res.trim();
return res;
}
BigInt operator*(int v) const {
if (llabs(v) >= BASE) return *this * BigInt(v);
BigInt res = *this;
res *= v;
return res;
}
BigInt operator*(const BigInt &v) const {
// TODO: Do we need to static_cast this?
if (a.size() < 32 || v.a.size() < 32) return mul_simple(v);
if (a.size() > 100111 || v.a.size() > 100111) return mul_fft(v);
return mul_karatsuba(v);
}
void operator*=(int v) {
if (llabs(v) >= BASE) {
*this *= BigInt(v);
return;
}
if (v < 0) this->sign = -sign, v = -v;
for (int i = 0, carry = 0; i < static_cast<int>(this->a.size()) || carry; ++i) {
if (i == static_cast<int>(this->a.size())) this->a.push_back(0);
long long cur = this->a[i] * static_cast<long long>(v) + carry;
carry = static_cast<int>(cur / BASE);
this->a[i] = static_cast<int>(cur % BASE);
}
trim();
}
void operator*=(const BigInt &v) { *this = *this * v; }
// ============ Division ============
friend pair<BigInt, BigInt> divmod(const BigInt &a1, const BigInt &b1) {
assert(b1 > 0); // TODO: Handle b1 <= 0
long long norm = BASE / (b1.a.back() + 1);
BigInt a = a1.abs() * norm;
BigInt b = b1.abs() * norm;
BigInt q = 0, r = 0;
q.a.resize(a.a.size());
for (int i = static_cast<int>(a.a.size()) - 1; i >= 0; --i) {
r *= BASE;
r += a.a[i];
long long s1 = r.a.size() <= b.a.size() ? 0 : r.a[b.a.size()];
long long s2 = r.a.size() <= b.a.size() - 1 ? 0 : r.a[b.a.size() - 1];
long long d = (static_cast<long long>(BASE) * s1 + s2) / b.a.back();
r -= b * d;
while (r < 0) r += b, --d;
q.a[i] = d;
}
q.sign = a1.sign * b1.sign;
r.sign = a1.sign;
q.trim();
r.trim();
auto res = make_pair(q, r / norm);
if (res.second < 0) res.second += b1;
return res;
}
BigInt operator/(int v) const {
assert(v > 0); // TODO: Handle v <= 0
if (llabs(v) >= BASE) return *this / BigInt(v);
BigInt res = *this;
res /= v;
return res;
}
BigInt operator/(const BigInt &v) const {
if (v < 0) return divmod(-*this, -v).first;
return divmod(*this, v).first;
}
void operator/=(int v) {
assert(v > 0); // TODO: Handle v <= 0
if (llabs(v) >= BASE) {
*this /= BigInt(v);
return;
}
if (v < 0) this->sign = -sign, v = -v;
for (int i = static_cast<int>(this->a.size()) - 1, rem = 0; i >= 0; --i) {
long long cur = this->a[i] + rem * static_cast<long long>(BASE);
this->a[i] = static_cast<int>(cur / v);
rem = static_cast<int>(cur % v);
}
trim();
}
void operator/=(const BigInt &v) { *this = *this / v; }
// ============ Modulo ============
BigInt operator%(const BigInt &v) const {
// TODO: Verify this
if (v < 0) return divmod(-*this, -v).second;
return divmod(*this, v).second;
}
long long operator%(long long v) const {
assert(v > 0); // TODO: Handle v <= 0
assert(v < BASE); // TODO: Handle v >= BASE
int m = 0;
for (int i = static_cast<int>(this->a.size()) - 1; i >= 0; --i) {
m = (this->a[i] + m * static_cast<long long>(BASE)) % v;
}
return m * this->sign;
}
// ============ Utility ============
BigInt abs(void) const {
BigInt res = *this;
res.sign *= res.sign;
return res;
}
void trim(void) {
while (!this->a.empty() && !this->a.back()) this->a.pop_back();
if (this->a.empty()) this->sign = 1;
}
bool isZero(void) const {
return this->a.empty() || (static_cast<int>(this->a.size()) == 1 && !this->a[0]);
}
friend BigInt gcd(const BigInt &a, const BigInt &b) {
return b.isZero() ? a : gcd(b, a % b);
}
friend BigInt lcm(const BigInt &a, const BigInt &b) {
return a / gcd(a, b) * b;
}
friend BigInt sqrt(const BigInt &a1) {
BigInt a = a1;
while (a.a.empty() || a.a.size() & 1) a.a.push_back(0);
int n = static_cast<int>(a.a.size());
int firstDigit = static_cast<int>(sqrt(static_cast<double>(a.a[n - 1]) * BASE + a.a[n - 2]));
int norm = BASE / (firstDigit + 1);
a *= norm;
a *= norm;
while (a.a.empty() || a.a.size() & 1) a.a.push_back(0);
BigInt r = static_cast<long long>(a.a[n - 1]) * BASE + a.a[n - 2];
firstDigit = static_cast<int>(sqrt(static_cast<double>(a.a[n - 1]) * BASE + a.a[n - 2]));
int q = firstDigit;
BigInt res;
for (int j = n / 2 - 1; j >= 0; --j) {
for (;; --q) {
BigInt r1 = (r - (res * 2 * BigInt(BASE) + q) * q) * BigInt(BASE) * BigInt(BASE) + (j > 0 ? static_cast<long long>(a.a[2 * j - 1]) * BASE + a.a[2 * j - 2] : 0);
if (r1 >= 0) {
r = r1;
break;
}
}
res *= BASE;
res += q;
if (j > 0) {
int d1 = res.a.size() + 2 < r.a.size() ? r.a[res.a.size() + 2] : 0;
int d2 = res.a.size() + 1 < r.a.size() ? r.a[res.a.size() + 1] : 0;
int d3 = res.a.size() < r.a.size() ? r.a[res.a.size()] : 0;
q = static_cast<int>((static_cast<long long>(d1) * BASE * BASE + static_cast<long long>(d2) * BASE + d3) / (firstDigit * 2));
}
}
res.trim();
return res / norm;
}
};
void solve(void) {
int n, m; cin >> n >> m;
BigInt ans = 1;
for (int i=0; i<m; i++) {
ans *= (n-i);
ans /= (i+1);
}
cout << ans;
}
int main(void) {
ios::sync_with_stdio(false);
cin.tie(nullptr);
solve();
return 0;
}