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#include <bits/stdc++.h>
#define ll long long
#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define vi vector<int>
#define pi pair<int, int>
#define mod 1000000007
template<typename T> bool chkmin(T &a, T b){return (b < a) ? a = b, 1 : 0;}
template<typename T> bool chkmax(T &a, T b){return (b > a) ? a = b, 1 : 0;}
ll ksm(ll a, ll b) {if (b == 0) return 1; ll ns = ksm(a, b >> 1); ns = ns * ns % mod; if (b & 1) ns = ns * a % mod; return ns;}
using namespace std;
int n, m;
const int maxn = 3005;
ll dp[maxn][maxn][2]; // a filled, b valid characters, valid or not
int main() {    
    cin >> n >> m;
    dp[0][0][1] = 1;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= i; j++)
            for (int k = 0; k < 2; k++) {
                // valid chara
                dp[i + 1][j][1] = (dp[i + 1][j][1] + dp[i][j][k] * j) % mod;
                dp[i + 1][j + k][0] = (dp[i + 1][j + k][0] + (m - j) * dp[i][j][k]) % mod;
            }
    }
    ll ans = 0;
    for (int j = 0; j <= n; j++)
        ans += dp[n][j][1];
    ans %= mod;
    if (ans < 0) ans += mod;
    cout << ans << endl;
    return (0-0); // <3 cxr
}