#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
//#pragma GCC target("popcnt")
using namespace __gnu_pbds;
using namespace std;
using ordered_set = tree<int, null_type, less_equal<>, rb_tree_tag, tree_order_statistics_node_update>;
#define popcount __builtin_popcountll
#define all(a) (a).begin(), (a).end()
const int MOD = 1e9+7;
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int h,w; cin >> h >> w;
long long dp[h+1][w+1] = {};
for (int i = 0; i <= h; i++) dp[i][0] = 1;
for (int j = 0; j <= w; j++) dp[0][j] = 1;
for (int i = 1; i <= h; i++) {
for (int j = 1; j <= w; j++) {
dp[i][j] = (dp[i-1][j] + dp[i-1][j-1] * 4*j) % MOD;
if (i >= 2)
(dp[i][j] += dp[i-2][j-1] * (i-1) * j % MOD) %= MOD;
if (j >= 2)
(dp[i][j] += dp[i-1][j-2] * j * (j-1) / 2) %= MOD;
}
}
cout << (MOD + dp[h][w] - 1) % MOD;
}
