1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
#include <bits/stdc++.h>
#define FOR(i, n) for(int i = 0; i < (n); ++i)
#define REP(i, a, b) for(int i = (a); i < (b); ++i)
#define TRAV(i, a) for(auto & i : (a))
#define SZ(x) ((int)(x).size())
#define X first
#define Y second
#define PR std::pair
#define MP std::make_pair
typedef long long ll;
typedef std::pair<int, int> PII;
typedef std::vector<int> VI;

constexpr int MOD = 1000000007;
int dp[3005][3005][2];

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

	int n, m;
	std::cin >> n >> m;
	FOR(i, n+1) dp[0][i][1] = 1;

	REP(i, 1, n+1){
		int upto = std::min(n, m);
		FOR(j, upto+1){
			dp[i][j][0] = (
				1ll * dp[i-1][j][1] * j +
				1ll * dp[i-1][j][0] * (m-j)
			) % MOD;

			dp[i][j][1] = (
				1ll * dp[i-1][j][1] * j +
				1ll * dp[i-1][j+1][0] * (m-j)
			) % MOD;
		}
	}

	std::cout << dp[n][0][1] << "\n";

	return 0;
}