#include<bits/stdc++.h>
#define ll long long
#define Re register
#define Il inline
#define rep(i,a,b) for(ll i=(a);i<=(b);i++)
#define drep(i,a,b) for(ll i=(a);i>=(b);i--)
#define go(u) for(ll i=head[u],v=e[i].to;i;i=e[i].nxt,v=e[i].to)
#define _go(u) for(ll i=Head[u],v=E[i].to;i;i=E[i].nxt,v=E[i].to)
#define writesp(x) write(x),putchar(' ')
#define writeln(x) write(x),puts("")
#define mem(x,v) memset(x,v,sizeof(x))
Il ll read(){ll sum=0,f=0;char ch=getchar();for(;!isdigit(ch);ch=getchar())f|=(ch=='-');for(;isdigit(ch);ch=getchar())sum=(sum<<1)+(sum<<3)+(ch^48);return f?-sum:sum;}
void write(ll x){if(x<0){putchar('-');write(-x);return;}if(x>=10)write(x/10);putchar(x%10+'0');}
char getc(){char ch=getchar();while(ch!='?'&&ch!='+'&&ch!='-')ch=getchar();return ch;}
using namespace std;
#define N 3300
ll f[N][N][2],n,m,mod=1e9+7;
int main(){
	n=read(),m=read();
	f[n+1][0][1]=1;
	drep(i,n,1)rep(j,0,m){
		f[i][j][1]=(f[i+1][j][0]+f[i+1][j][1])*j%mod;
		f[i][j][0]=f[i+1][j][0]*(m-j)%mod;if(j)f[i][j][0]=(f[i][j][0]+f[i+1][j-1][1]*(m-j+1))%mod;
	}
	ll ans=0;
	rep(i,1,m)ans=(ans+f[1][i][1])%mod;
	writeln(ans);
}