#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 3e3 + 2;
const int mod = 1e9 + 7;
int Add(int a, int b) {
a += b;
if (a >= mod) a -= mod;
if (a < 0) a += mod;
return a;
}
int Mul(int a, int b) {
ll c = a; c *= b; c %= mod;
return c;
}
bool was[N][N];
int dp[N][N];
int Solve(int a, int b) {
if (a <= 0 || b <= 0) return 1;
if (a == 1 && b == 1) return 5;
if (was[a][b]) return dp[a][b];
was[a][b] = 1;
int ans = Solve(a - 1, b);
ll k = 4 * b;
ans = Add(ans, Mul(Solve(a - 1, b - 1), k));
k = b * (b - 1) / 2;
ans = Add(ans, Mul(Solve(a - 1, b - 2), k));
k = (a - 1) * b;
ans = Add(ans, Mul(Solve(a - 2, b - 1), k));
return dp[a][b] = ans;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int h, w; cin >> h >> w;
cout << Add(Solve(h, w), -1) << en;
return 0;
}
