#include <bits/stdc++.h>
#define f first
#define s second
#define pb push_back
#define pp pop_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
#define rep(a, b, c) for (int a = (b); (a) <= (c); ++a)
#define per(a, b, c) for (int a = (b); (a) >= (c); --a)
#define nl '\n'
#define ioi exit(0);
using namespace std;
typedef long long ll;
const int MAX_N = (int)1e5 + 7;
const int mod = (int)1e9 + 7;
int n, k;
int f[MAX_N], rv[MAX_N];
int bp(int x, int y) {
int res = 1;
while (y) {
if (y & 1) res = res * 1ll * x % mod;
x = x * 1ll * x % mod, y >>= 1;
}
return res;
}
int cnk(int x, int y) {
return ((f[x] * 1ll * rv[x - y]) % mod) * 1ll * rv[y] % mod;
}
int main() {
#ifdef IOI
freopen ("in.txt", "r", stdin);
#endif
cin >> n >> k;
/* rep(i, 0, n + 1) {
c[i][0] = 1;
rep(j, 1, i) {
c[i][j] = (c[i - 1][j] + c[i - 1][j - 1]) % mod;
}
} */
f[0] = rv[0] = 1;
rep(i, 1, n + 1) {
f[i] = f[i - 1] * 1ll * i % mod;
rv[i] = bp(f[i], mod - 2);
}
int ans = 0;
k--;
rep(i, 0, k) {
int x = bp(-1, i) * 1ll * cnk(n + 1, i) % mod;
x = x * 1ll * bp(k - i + 1, n) % mod;
ans += x;
ans %= mod;
ans += mod;
ans %= mod;
}
cout << ans;
//cout << dp[n][k];
ioi
}
