#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MOD = 1000000007;
const int MAXH = 3005;
const int MAXW = 3005;
int dp[MAXW][MAXH], ds[MAXW][MAXH], dks[MAXW][MAXH];
int H, W;
int main() {
for(int i = 0; i < MAXH; i++) dp[0][i] = dp[i][0] = 1;
for(int i = 0; i < MAXH; i++) ds[0][i] = i+1;
dks[0][0] = 1; for(int i = 1; i < MAXH; i++) dks[0][i] = (dks[0][i-1] + i+1) % MOD;
cin >> H >> W;
for(int w = 1; w <= W; w++) {
for(int h = 1; h <= H; h++) {
int &ret = dp[w][h];
ret = (ll(ds[w-1][h-1]) * w % MOD * 4 + ret) % MOD;
if(1 < h) ret = (ll(dks[w-1][h-2]) * w + ret) % MOD;
if(1 < w) ret = (ll(w) * (w-1) / 2 % MOD * ds[w-2][h-1] + ret) % MOD;
ret = (ret + 1) % MOD;
}
ds[w][0] = 1; for(int j = 1; j <= H; j++) ds[w][j] = (ds[w][j-1] + dp[w][j]) % MOD;
dks[w][0] = 1; for(int j = 1; j <= H; j++) dks[w][j] = (ll(dp[w][j]) * (j+1) + dks[w][j-1]) % MOD;
}
cout << ((dp[W][H] - 1 + MOD) % MOD) << endl;
return 0;
}
