#include<bits/stdc++.h>
#define st first
#define nd second
#define mp make_pair
#ifndef LOCAL
#define cerr if(0)cerr
#endif
using namespace std;
using ll = long long;
using ld = long double;
using vi = vector<int>;
using pii = pair<int, int>;
const ll mod = 1e9+7, inv2 = (mod+1)/2;
const int MAXH = 3001;
ll factorial[MAXH], C[MAXH][MAXH];
ll fpow(ll x, ll p) {
if(p==0LL) return 1LL;
ll y = fpow(x, p/2);
if(p%2==0) {
return y*y % mod;
}
return y*y % mod * x % mod;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int H, W; cin>>H>>W;
factorial[0] = 1;
for(int i=1; i<=max(H, W); ++i) {
factorial[i] = factorial[i-1] * i % mod;
}
C[0][0] = 1;
for(int i=1; i<=max(H, W); ++i) {
C[i][0] = C[i][i] = 1;
for(int j=1; j<i; ++j) {
C[i][j] = C[i-1][j-1] + C[i-1][j];
}
}
vector<vector<ll>> dp(H+1, vector<ll>(W+1));
dp[0][0] = 1;
for(int i=1; i<=H; ++i) {
dp[i][0] = 1;
for(int j=1; j<=W; ++j) {
dp[i][j] = (dp[i-1][j] + dp[i-1][j-1] * (W - (j-1)) % mod * 4 % mod) % mod;
if(i>=2) { //column
dp[i][j] = (dp[i][j] + dp[i-2][j-1] * (H-(i-1)) % mod * (W-(j-1)) % mod) % mod;
}
if(j>=2) { //row
dp[i][j] = (dp[i][j] + dp[i-1][j-2] * ((W-(j-2)) * (W-(j-1)) / 2) % mod) % mod;
}
}
}
ll ans = 0;
for(int j=1; j<=W; ++j) {
ans = (ans + dp[H][j]) % mod;
}
cout<<ans<<'\n';
}
