#include <iostream>
#include <vector>
#include <algorithm>
#include <cassert>
using ll = long long;
#define debug(x) #x << " = " << x << '\n'
const int mod = 1e9 + 7;
const int MAXN = 1e5;
int fac[MAXN + 1];
int ifac[MAXN + 1];
int power(int a, int b) {
int ret = 1;
while (b) {
if (b & 1) {
ret = (ll) ret * a % mod;
}
a = (ll) a * a % mod;
b >>= 1;
}
return ret;
}
int C(int n, int k) {
return (ll) fac[n] * ifac[k] % mod * ifac[n - k] % mod;
}
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(0);
int n, k;
std::cin >> n >> k;
fac[0] = 1;
for (int i = 1; i <= n + 1; i++) {
fac[i] = (ll) fac[i - 1] * i % mod;
}
ifac[n + 1] = power(fac[n + 1], mod - 2);
for (int i = n; i >= 0; i--) {
ifac[i] = (ll) ifac[i + 1] * (i + 1) % mod;
}
ll answer = 0;
for (int i = 0; i <= k; i++) {
if (i & 1) {
answer -= (ll) C(n + 1, i) * power(k - i, n) % mod;
} else {
answer += (ll) C(n + 1, i) * power(k - i, n) % mod;
}
}
answer += (ll) mod * mod;
std::cout << answer % mod;
return 0;
}
