#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
const int mod = 1e9 + 7;
int fac[maxn], revfac[maxn];
ll power(ll a, ll b){
if (b == 0)
return 1;
ll ret = power(a, b / 2);
ret = 1ll * ret * ret % mod;
if (b & 1)
return ret * a % mod;
return ret;
}
ll C(int n, int r){
return 1ll * fac[n] * revfac[r] % mod * revfac[n - r] % mod;
}
int main(){
ios_base::sync_with_stdio(false);
int n, m;
cin >> n >> m;
fac[0] = 1;
for (int i = 1; i <= n + 1; i++)
fac[i] = 1ll * fac[i - 1] * i % mod;
revfac[n + 1] = power(fac[n + 1], mod - 2);
for (int i = n; i >= 0; i--)
revfac[i] = 1ll * revfac[i + 1] * (i + 1) % mod;
ll answer = 0;
int sign = 1;
for (int k = 0; k <= m; k++){
ll t = 1ll * sign * C(n + 1, k) * power(m + 1 - k, n) % mod;
answer = (answer + t + mod) % mod;
sign *= -1;
}
cout << answer << endl;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |