/* _In The Name Of God_ */
#include <bits/stdc++.h>
using namespace std;
#define maxs(a, b) a = max(a, b)
#define mins(a, b) a = min(a, b)
#define pb push_back
#define F first
#define S second
#define lc id << 1
#define rc lc|1
#define mid ((l + r)/2)
#define int long long
typedef pair<int, int> pii;
typedef long long ll;
const ll MOD = 1e9 + 7; // 998244353;
const ll INF = 1e9 + 1;
const int MXN = 3e3 + 5;
const int LOG = 23;
ll Pow(ll a, ll b) { return !b ? 1 : (Pow(a*a %MOD, b/2) * (b&1 ? a : 1)) %MOD; }
int dp[2][MXN][MXN], n, m, C[MXN][MXN];
void _solve() {
cin >> n >> m;
dp[0][0][0] = dp[1][0][0] = 1;
C[0][0] = 1;
for (int i = 1; i <= max(n, m); i++) dp[0][0][i] = dp[0][i][0] = C[i][0] = 1;
for (int i = 1; i <= max(n, m); i++) {
for (int j = 1; j <= i; j++) {
if (i >= j) C[i][j] = (C[i-1][j] + C[i-1][j-1]) % MOD;
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
dp[0][i][j] += dp[0][i-1][j] + 4ll * j * dp[0][i-1][j-1] % MOD;
dp[0][i][j] %= MOD;
if (j >= 2)
(dp[1][i][j] += dp[1][i-1][j-2] * j * (j-1) / 2) %= MOD;
if (i >= 2)
(dp[1][i][j] += dp[1][i-2][j-1] * (i-1) * j) %= MOD;
}
}
ll ans = 0;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= m; j++) {
(ans += dp[0][i][j] * dp[1][n-i][m-j] % MOD * C[n][i] % MOD * C[m][j] % MOD) %= MOD;
}
}
cout << (ans-1+MOD)%MOD << '\n';
}
int32_t main() {
cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
int _ = 1;
// cin >> _;
while (_--) _solve();
return 0.0;
}
