#include<bits/stdc++.h>
#define int long long
#define pii pair<int, int>
using namespace std;
const int MOD=1e9+7;
signed main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
vector<vector<int>> dp(n+1, vector<int>(m+1));
vector<vector<int>> pre(n+1, vector<int>(m+1));
dp[0][0]=1;
for(int i=1; i<=n; i++) dp[i][0]=1;
for(int j=1; j<=m; j++) dp[0][j]=1;
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++) {
if(i>=2) dp[i][j]=(dp[i][j]+i*(i-1)/2*dp[i-2][j-1])%MOD;
if(j>=2) dp[i][j]=(dp[i][j]+i*(j-1)*dp[i-1][j-2])%MOD;
dp[i][j]=(dp[i][j]+4LL*i*dp[i-1][j-1]%MOD)%MOD;
dp[i][j]=(dp[i][j]+dp[i][j-1])%MOD;
}
}
cout << dp[n][m]-1 << '\n';
return 0;
}
