#include<bits/stdc++.h>
using namespace std;
typedef long double ld;
typedef long long ll;
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
const ll MOD=1e9+7;
const int LIM=3e3+7;
ll dp[LIM][LIM];
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int h, w;
cin >> h >> w;
rep(i, h+1) dp[i][0]=1;
rep(i, w+1) dp[0][i]=1;
for(int n=1; n<=h; ++n) for(int m=1; m<=w; ++m) {
ll a=dp[n-1][m];
ll b=(dp[n-1][m-1]*4*m)%MOD;
ll c=0;
if(m>=2) c=(dp[n-1][m-2]*((m*(m-1)/2)%MOD))%MOD;
ll d=0;
if(n>=2) d=(dp[n-2][m-1]*((m*(n-1))%MOD))%MOD;
dp[n][m]=(a+b+c+d)%MOD;
}
ll ans=(dp[h][w]-1+MOD)%MOD;
cout << ans << '\n';
}
