// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
using namespace std;
#define nl '\n'
#define pb push_back
#define pf push_front
#define mp make_pair
#define f first
#define s second
#define sz(x) int(x.size())
template<class T> using V = vector<T>;
using pi = pair<int, int>;
using vi = V<int>;
using vpi = V<pi>;
using ll = long long;
using pl = pair<ll, ll>;
using vpl = V<pl>;
using vl = V<ll>;
using db = long double;
template<class T> using pq = priority_queue<T, V<T>, less<T>>;
const int MOD = 1e9 + 7;
const ll INFL = ll(1e17);
const int LG = 19;
int main() {
cin.tie(0)->sync_with_stdio(0);
int H, W; cin >> H >> W;
V<vl> dp(H+1, vl(W+1, 0));
for(int r = 0; r <= H; r++) for(int c = 0; c <= W; c++) {
if (r == 0 || c == 0) dp[r][c] = 1;
else {
dp[r][c] = (dp[r-1][c] + dp[r-1][c-1] * 4LL * c) % MOD;
if (r >= 2) {
dp[r][c] += (dp[r-2][c-1] * (r - 1) * 1LL * c) % MOD;
dp[r][c] %= MOD;
}
if (c >= 2) {
dp[r][c] += (dp[r-1][c-2] * (c * 1LL * (c - 1)) / 2) % MOD;
dp[r][c] %= MOD;
}
}
}
dp[H][W] -= 1;
cout << (dp[H][W] + MOD) % MOD << nl;
exit(0-0);
}
