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#include<algorithm>
#include<iostream>
#include<vector>

using namespace std;
using VI  = vector<long long>;
using VVI = vector<VI>;

constexpr int mod = int(1e9 + 7);

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);

	long long n, m; cin >> n >> m;
	long long c = min((n + 1) / 2, m); 

	VVI loop(n + 1, VI(c + 1, 0));
	VVI dp(n + 1, VI(c + 1, 0));
	dp[1][1] = m; loop[1][1] = 0;
	for (int i = 2; i <= n; i++) {
		for (int j = 1; j <= c; j++) {
			dp[i][j] += (dp[i - 1][j] - loop[i - 1][j] + mod) * (m - j);
			dp[i][j] += dp[i - 1][j] * j;
			dp[i][j] += loop[i - 1][j - 1] * (m - j + 1);
			dp[i][j] %= mod;
			loop[i][j] = (dp[i - 1][j] * j) % mod;
		}
	}
	long long ans = 0;
	for (int j = 1; j <= c; j++)
		ans += loop[n][j];
	ans %= mod;
	cout << ans << "\n";
}