#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<int, int> pii;
typedef pair<ld, ld> pld;
const ll mod = 1e9+7;
ll n, m;
ll dp[3009][3009];
ll f(ll x, ll y){
if(x < 0 || y < 0) return 0;
if(dp[x][y] != 0) return dp[x][y];
if(x == 0 || y == 0) return dp[x][y] = 1;
dp[x][y] = y*(y-1)/2*f(x-1, y-2)%mod + y*(x-1)*f(x-2, y-1)%mod + 4*y*f(x-1, y-1)%mod + f(x-1, y);
dp[x][y] %= mod;
return dp[x][y];
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
//freopen("in.txt", "r", stdin);
//freopen("out.txt", "w", stdout);
cin >> n >> m;
cout << f(n, m)-1 << '\n';
}
