문제

링크

풀이

#include <iostream>
#include <vector>
using namespace std;
 
bool solve(void) {
  int m, n; cin >> m >> n;
 
  vector<bool> v(m, false);
  while (n--) {
    int l, r; cin >> l >> r; l--; r--;
    for (int j=l; j<=r; j++) v[j] = true;
  }
 
  for (int i=0; i<m; i++) {
    if (!v[i]) return false;
  }
  return true;
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  cout << (solve() ? "YES" : "NO");
  return 0;
}