#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=5005,M=1e9+7;
int n,m,g[N][N],f[N][N],fac[N],inv[N];
inline int ksm(int x,int y){
	int ans=1;
	for (;y;y>>=1,x=x*x%M)
		if (y&1)(ans*=x)%=M;
	return ans;
}
signed main(){
	scanf("%lld%lld",&m,&n);
	fac[0]=inv[0]=1;
	for (int i=1;i<N;i++)fac[i]=fac[i-1]*2%M,inv[i]=ksm(fac[i],M-2);
	for (int i=1;i<=n;i++)f[0][i]=1,g[0][i]=(g[0][i-1]+inv[i+1]*i)%M;
	for (int i=1;i<=m;i++)
		for (int j=1;j<=n;j++){
			(f[i][j]+=g[i-1][j-1]*fac[j]+f[i-1][j]*(j+1))%=M;
			(g[i][j]+=g[i][j-1]+f[i][j]*inv[j+1]%M*j)%=M;
		}
	printf("%lld\n",f[m][n]);
}
 
