#include <bits/stdc++.h>
using namespace std;
long mod = 0;
long getDublicatedPatterns(int cubes, int colors);
inline long getCombination(int all, int select);
int main(){
    int n,m;
    cin >> n;
    cin >> m;
    //s << "n " << n << " m " << m << endl;
    int numInkBottol = m;
    int numWanabePainted =n;
    long patterns = 1;
    mod = (long)pow(10,9)+7;

    //long tmp = getCombination(45,43);
    //cout << tmp << endl;
    //return 0;

    if (numWanabePainted > numInkBottol) {

        patterns = getDublicatedPatterns(numWanabePainted,numInkBottol);
        //cout << patterns << endl;
        int plusMinus = 1;
        for(int i = numInkBottol;i > 0; i--){
            patterns = patterns - (plusMinus * getCombination(numInkBottol,i -1) * getDublicatedPatterns(numWanabePainted,i-1));
            patterns = patterns % mod;
            plusMinus *= -1;
            //cout <<"i " <<i << " pattern "<<patterns << endl;
        }
        if(patterns < 0){
            patterns = mod + patterns;
        }

    }else{
        //インクの種類が十分多い
        //順番にインクのバケツにいれる。
        for (int i = numInkBottol; i > 0; i--){
            patterns = patterns * i;
            patterns = patterns % mod;
        }
    }
    cout << patterns << endl;
}
inline long getDublicatedPatterns(int cubes, int colors){
    long ret = 1;
    for(int i = cubes;i>0;i--){
        ret = ret*colors;
        ret = ret % mod;
        //cout << "i " << i << " colors " <<colors << " ret " << ret << endl;
    }
    //cout << "colors " <<colors << " ret " << ret << endl;
    return ret;
}
inline long getCombination(int all, int select){
    long ret = 1;
    vector <int> top;
    vector <int> bottom;
    for(int i = select;i > 0; i--){
        top.push_back(all-(select-i));
        bottom.push_back(i);
    }
    for(int i = 0; i < select;i++){
        //cout << " " << top[i];
    }
    //cout << endl;
    for(int i = 0; i < select;i++){
        //cout << " " << bottom[i];
    }
    //cout << endl;
    for(int i = 0; i< select;i++){
        if(bottom[i]!=1){
            for(int j =0 ; j < select; j++){
                if(top[j]%bottom[i]==0){
                    top[j] = (top[j]/bottom[i]);
                    bottom[i] = 1;
                }
            }
        }
    }
    long topTmp = 1;
    long bottomTmp = 1;
    for(int i = 0; i < select;i++){
        //cout << " " << top[i];
        topTmp*=top[i];
        bottomTmp*=bottom[i];
        topTmp %= mod;
        bottomTmp %= mod;
    }
    //cout << endl;
    for(int i = 0; i < select;i++){
        //cout << " " << bottom[i];
    }
    //cout << bottomTmp << endl;
    ret = topTmp/bottomTmp;

    //cout << "conbination " << ret << " all " << all << " select " << select<<  endl;
     return ret;
}