#include<bits/stdc++.h>
using namespace std;
const int N=5e3+10;
const int mod=1e9+7;
const int inv2=(mod+1)>>1;

int gi() {
	int x=0,o=1;char ch=getchar();
	while(!isdigit(ch)&&ch!='-') ch=getchar();
	if(ch=='-') o=-1,ch=getchar();
	while(isdigit(ch)) x=x*10+ch-'0',ch=getchar();
	return x*o;
}

int n,m,f[N][N],bin[N],ibin[N];

int main() {
	cin>>n>>m;
	bin[0]=1;for(int i=1;i<N;i++) bin[i]=(bin[i-1]<<1)%mod;
	ibin[0]=1;for(int i=1;i<N;i++) ibin[i]=1ll*ibin[i-1]*inv2%mod;
	for(int i=0;i<=n;i++) {
		int sum=0;
		for(int j=0;j<=m;j++) {
			if(i==0||j==0) f[i][j]=1;
			else {
				f[i][j]=(1ll*f[i-1][j]*(j+1)+1ll*bin[j-1]*sum)%mod;
			}
			if(j) sum=(sum+1ll*f[i-1][j]*j%mod*ibin[j])%mod;
		}
	}
	cout<<f[n][m];
	return 0;
}
