#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
#define all(x) (x).begin(),(x).end()
#define X first
#define Y second
#define sep ' '
#define endl '\n'
#define SZ(x) ll(x.size())
const ll MAXN = 3010;
const ll LOG = 22;
const ll INF = 8e18;
const ll MOD = 1e9 + 7; //998244353; //1e9 + 9;
ll n , m , dp[MAXN][MAXN];
int main() {
ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
cin >> n >> m;
for(int i = 0 ; i <= n ; i++){
for(int j = 0 ; j <= m ; j++){
if(i == 0 || j == 0){
dp[i][j] = 1;
continue;
}
dp[i][j] = dp[i - 1][j];
dp[i][j] += 4 * j * dp[i - 1][j - 1];
if(j > 1) dp[i][j] += j * (j - 1) / 2 * dp[i - 1][j - 2];
if(i > 1) dp[i][j] += j * (i - 1) * dp[i - 2][j - 1];
dp[i][j] %= MOD;
}
}
cout << (dp[n][m] + MOD - 1) % MOD << endl;
return 0;
}
/*
*/
