// Parsa Jokar 2023 https://github.com/phictus/ioi
#pragma GCC optimize("Ofast")
#include <iostream>
#include <cstdint>
using namespace std;
constexpr int64_t maxn = 3000, mod = 1000000007;
int64_t n, m, dp[maxn + 1][maxn + 1];
int main()
{
ios_base::sync_with_stdio(false);
cin >> n >> m;
for (int64_t i = 0; i <= n; i++)
dp[i][0] = 1;
for (int64_t j = 0; j <= m; j++)
dp[0][j] = 1;
for (int64_t i = 1; i <= n; i++)
dp[i][1] = 1 + 4 * i + (i * (i - 1)) / 2;
for (int64_t j = 1; j <= m; j++)
dp[1][j] = 1 + 4 * j + (j * (j - 1)) / 2;
for (int64_t i = 2; i <= n; i++)
{
for (int64_t j = 2; j <= m; j++)
{
dp[i][j] = dp[i][j - 1] + 4 * i * dp[i - 1][j - 1] + i * (j - 1) * dp[i - 1][j - 2] + (i * (i - 1) / 2) * dp[i - 2][j - 1];
dp[i][j] %= mod;
}
}
cout << dp[n][m] - 1 << '\n';
return (0 ^ 0);
}
