#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
#define pb push_back
#define f first
#define s second
const int MAXN = 1e5 + 10;
const ll MOD = 1e9 + 7;
ll fact[MAXN];
ll iFact[MAXN];
ll comb(int n, int k) {
return fact[n] * iFact[k] % MOD * iFact[n - k] % MOD;
}
ll binExp(ll base, int exp) {
base %= MOD;
ll prod = 1;
while (exp > 0) {
if (exp & 1) {
prod = prod * base % MOD;
}
base = base * base % MOD;
exp >>= 1;
}
return prod;
}
int main() {
fact[0] = 1;
for (int i = 1; i < MAXN; i++) {
fact[i] = fact[i - 1] * i % MOD;
}
iFact[MAXN - 1] = 549915853;
assert(fact[MAXN - 1] * iFact[MAXN - 1] % MOD == 1);
for (int i = MAXN - 2; i >= 0; i--) {
iFact[i] = (i + 1) * iFact[i + 1] % MOD;
assert(fact[i] * iFact[i] % MOD == 1);
}
// cout << comb(23134, 242) << endl;
// cout << binExp(2342, 124515) << endl;
int N, K;
cin >> N >> K;
K--;
ll sum = 0;
for (int i = 0; i <= K; i++) {
ll val = comb(N + 1, i) * binExp(K + 1 - i, N) % MOD;
// cout << val << endl;
if (i % 2 == 0) {
sum = (sum + val) % MOD;
} else {
sum = (sum - val + MOD) % MOD;
}
}
cout << sum << endl;
}
