/*////////ACACACACACACAC///////////
       . Coding by Ntsc .
       . ToFind Chargcy .
       . Prove Yourself .
/*////////ACACACACACACAC///////////

//头文件
#include<bits/stdc++.h>

//数据类型
#define int long long
#define ull unsigned long long
#define db double
#define endl '\n'
//命名空间
using namespace std;
//常量
const int N=5e5+5;
const int M=1e3;
const int MOD=1e9+7;
const int INF=1e9;
//变量
int n,m,a,b,c,x[N],y[N],ans,res,tmp,cnt,web[M][M],fac[N];

int ksm(int c,int k,int p) {	//c^k %p
	int res=1;
	while(k) {
		if(k&1) {
			res=res*c%p;	//注意只有1句在里面！
		}
		k>>=1;	//不要写反了！
		c=c*c%p;
	}
	return res;
}

int inv(int x){
    return ksm(x,MOD-2,MOD);
} 

int C(int n,int m){return fac[n]*inv(fac[m])%MOD*inv(fac[n-m])%MOD;}

int A(int n,int m){return fac[n]*inv(fac[n-m])%MOD;}

signed main(){
    cin>>n>>m;
	fac[0]=1;
	for (int i=1;i<=m;++i) fac[i]=fac[i-1]*i%MOD;

	for (int i=0;i<=n;++i){
		int x=C(n,i)*A(m,i)%MOD*A(m-i,n-i)%MOD*A(m-i,n-i)%MOD;
		if(i&1)ans-=x;
        else ans+=x;
        ans%=MOD;
		ans+=MOD;ans%=MOD;
	}
    printf("%lld\n",ans);
#ifdef PAUSE_ON_EXIT
    system("pause");
#endif
    return 0;
}