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#include<bits/stdc++.h>

using namespace std;

constexpr int MAX_N = 3000;
constexpr int MOD = 1000000007;

int n,m,k[2];
long long wyn[2][2][MAX_N+9];

int main() {
	scanf("%d%d", &n, &m);
	wyn[1][0][1] = m;
	k[0] = 1;
	for(int i = 2; i <= n; ++i) {
		for(int j = 0; j <= k[i&1]; ++j) {
			wyn[i&1][0][j] = 0;
			wyn[i&1][1][j] = 0;
		}
		for(int j = 1; j <= k[i&1]; ++j) {
			wyn[i&1][1][j] += wyn[1^i&1][0][j] * j;
			wyn[i&1][0][j] += wyn[1^i&1][0][j] * (m-j);
			wyn[i&1][1][j] += wyn[1^i&1][1][j] * j;
			wyn[i&1][0][j+1] += wyn[1^i&1][1][j] * (m-j);
			wyn[i&1][0][j] %= MOD;
			wyn[i&1][1][j] %= MOD;
			wyn[i&1][0][j+1] %= MOD;
		}
		if(wyn[i&1][0][k[i&1]+1] > 0) {
			k[1^i&1] = k[i&1]+1;
		}
		else {
			k[1^i&1] = k[i&1];
		}
	}
	
	long long ret = 0;
	for(int i = 0; i <= n; ++i) {
		ret += wyn[n&1][1][i];
		ret %= MOD;
	}
	printf("%lld\n", ret);
	return 0;
}