#include <bits/stdc++.h>
#define int long long
using namespace std;
int memo[3005][3005];
const int mod = 1000000007;
int dp(int H, int W){ ///ways such that the topmost row and rightmost column are occupied
if(W < 0 || W < 0) return 0;
if(W == 0 || H == 0) return 1;
if(memo[H][W] != -1) return memo[H][W];
int ans = 0;
if(H == 1){
ans = 4*W + 1;
ans += (W-1)*W/2;
return ans;
}
///new row is empty
ans += dp(H-1,W);
///new row is 1 thing facing nothing
ans += 4*dp(H-1,W-1)*W;
///new row is 2 things facing each other
ans += dp(H-1,W-2) * (W) * (W-1) / 2;
///new row is south, and north is somwhere below
ans += dp(H-2, W-1) * W * (H-1);
ans %= mod;
memo[H][W] = ans;
return ans;
}
signed main(){
int H, W; cin >> H >> W;
memset(memo, -1, sizeof(memo));
int ans = dp(H,W);
ans--;
if(ans < 0) ans += mod;
cout << ans;
}
