#include "bits/stdc++.h"
using namespace std;
const int maxn = 3005;
const int mod = 1e9 + 7;
int w, h;
int f[maxn][maxn];
int add(int x, int y) {
if(y < 0) y += mod;
x = x + y;
if(x >= mod) x -= mod;
return x;
}
int c2(int x) {
return 1ll * x * (x - 1) / 2 % mod;
}
void solve() {
cin >> h >> w;
for(int i = 0; i <= h; ++i) f[i][0] = 1;
for(int i = 0; i <= w; ++i) f[0][i] = 1;
for(int i = 1; i <= h; ++i) {
for(int j = 1; j <= w; ++j) {
// add one tent
f[i][j] = 1ll * f[i - 1][j - 1] * j % mod * 4 % mod;
// add two tents in same row
f[i][j] = add(f[i][j], 1ll * f[i - 2][j - 1] * (i - 1) % mod * j % mod);
// add two tents in same col
f[i][j] = add(f[i][j], 1ll * f[i - 1][j - 2] * c2(j) % mod);
// do nothing
f[i][j] = add(f[i][j], f[i - 1][j]);
}
}
cout << add(f[h][w], -1);
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
