#include<bits/stdc++.h>
#define int long long
#define ll long long
using namespace std;
/*
pair<int,int> operator +(pair<int,int> l, pair<int,int> r){
	int l1=l.first, l2=l.second;
	int r1=r.first, r2=r.second;
	return 
}
*/


int32_t main(){

	ios::sync_with_stdio(false);
	cin.tie(NULL);
	
	int n,k;cin>>n>>k;
	
	vector<pair<int,int>> Dp(n+5,{0,0});Dp[1]={k,0};
	int M=1000000007;
	
	for(int i=2;i<=n;i++) {
		for(int j=i+1; j>0;j--){	
		Dp[j]={((k-j)*Dp[j].first%M + (k-j+1)*Dp[j-1].second%M)%M,( j*Dp[j].first%M + j*Dp[j].second%M)%M};
	
	
		}
	/*	cout << i<<":    ";
		for(int i2=0; i2 < i+1;i2++){
			cout <<i2<<":"<< Dp[i2].first<< ","<< Dp[i2].second<<"    ";
		}
		cout << endl;*/
	}
	
	int res=0;
	for(int i=0;i<n;i++)res=(res+Dp[i].second)%M;
	cout << res;
	
	
}