#include <iostream>
#include <cstring>
using namespace std;
#define ll long long
#define MOD 1000000007
ll dp[3005][3005];
ll go(int x, int y)
{
if(x == 0 || y == 0)
return 1;
ll& ret = dp[x][y];
if(ret != -1)
return ret;
ret = 0;
ret += go(x-1, y);
ret %= MOD;
if(y > 0)
ret += 4*y*go(x-1, y-1) % MOD;
ret %= MOD;
if(x > 1 && y > 0)
ret += (x-1)*y*go(x-2, y-1) % MOD;
ret %= MOD;
if(y > 1)
ret += (y*(y-1))/2 % MOD * go(x-1, y-2);
ret %= MOD;
return ret;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
memset(dp, -1, sizeof(dp));
int h, w;
cin >> h >> w;
cout << (go(h, w) - 1 + MOD) % MOD << '\n';
}
