#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const long long N = 3010;
long long dp[N][N];
long long Recur(long long row, long long col) {
if(row < 0 || col < 0)
return 0;
if(row == 0 || col == 0)
return 1;
if(dp[row][col] != -1)
return dp[row][col];
long long ans = 0, temp = 0;
//the row is empty
temp = Recur(row, col - 1);
ans = temp;
//1 tent facing anywhere
temp = ((Recur(row - 1, col - 1) * row) % MOD * 4) % MOD;
ans = (ans + temp) % MOD;
//2 tents facing each other (row-wise)
temp = (Recur(row - 2, col - 1) * (((row * (row - 1)) / 2) % MOD)) % MOD;
ans = (ans + temp) % MOD;
//2 tents facing each other (column-wise)
temp = (Recur(row - 1, col - 2));
long long x = row * (col - 1) % MOD;
temp *= x;
temp %= MOD;
ans = (ans + temp) % MOD;
dp[row][col] = ans;
return ans;
}
void Solve() {
long long n, m;
cin >> n >> m;
for(long long i = 0; i <= n; i++) {
for(long long j = 0; j <= m; j++) {
dp[i][j] = -1;
}
}
long long ans = Recur(n, m) - 1;
if(ans < 0)
ans += MOD;
cout << ans << endl;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
Solve();
return 0;
}
