#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
const int MAXN = 3e3 + 10;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
int n, m;
long long dp[MAXN][MAXN];
long long mod = 1e9 + 7;
void solve()
{
cin >> n >> m;
for (int i = 0; i <= n; ++ i)
dp[i][0] = 1;
for (int j = 0; j <= m; ++ j)
dp[0][j] = 1;
for (long long i = 1; i <= n; ++ i)
{
for (long long j = 1; j <= m; ++ j)
{
/// 0.
dp[i][j] = dp[i-1][j];
/// 1. x .... x
if(j >= 2)
{
dp[i][j] += (dp[i-1][j-2] * ((j * (j - 1) / 2) % mod)) % mod;
dp[i][j] %= mod;
}
/// 2. x
/// .
/// .
/// x
if(i >= 2)
{
dp[i][j] += dp[i-2][j-1] * (i-1) * j;
dp[i][j] %= mod;
}
/// 3. x
dp[i][j] += (dp[i-1][j-1] * j * 4) % mod;
dp[i][j] %= mod;
}
}
long long ans = (dp[n][m] + mod - 1) % mod;
cout << ans << endl;
}
int main()
{
speed();
solve();
return 0;
}
