#include <bits/stdc++.h>
using namespace std;
const int N = 200'000 + 10,
M = 1'000'000'007;
int n, k;
inline int powder(int a, int b) {
int ret = 1;
for (; b; b /= 2, a = 1ll * a * a % M) {
if (b & 1) ret = 1ll * ret * a % M;
}
return ret;
}
int fac[N], ifac[N];
inline int C(int n, int k) { return 1ll * fac[n] * ifac[n - k] % M * ifac[k] % M; }
int32_t main() {
cin.tie(0)->sync_with_stdio(0);
{ // init
fac[0] = 1;
for (int i = 1; i < N; ++i) fac[i] = 1ll * fac[i - 1] * i % M;
ifac[N - 1] = powder(fac[N - 1], M - 2);
for (int i = N - 1; i >= 1; --i) ifac[i - 1] = 1ll * ifac[i] * i % M;
}
cin >> n >> k;
int answer = 0;
for (int i = 0; i < k; ++i) {
int cnt = 1ll * C(n + 1, i) * powder(k - i, n) % M;
if (i & 1) answer = (answer + M - cnt) % M;
else answer = (answer + cnt) % M;
}
cout << answer << "\n";
}
