문제
풀이
#include <iostream>
#include <vector>
using namespace std;
int solve(void) {
int n, k; cin >> n >> k;
vector<int> a(n);
for (int i=0; i<n; i++) cin >> a[i];
int ans = 0;
for (int i=1; i<n; i++) {
if (a[i] > a[i-1]) continue;
else if (a[i] + k > a[i-1]) {
a[i] += k;
ans++;
} else return -1;
}
return ans;
}
int main(void) {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout << solve();
return 0;
}