#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF = (int) 1e9 + 1e6 + 123;
const ll LINF = (ll) 1e18 + 1e9 + 123;
#define rep(i, s, t) for (auto i = (s); i < (t); ++(i))
#define per(i, s, t) for (auto i = (s); i >= (t); --(i))
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define mp make_pair
#define pb push_back
bool mini(auto &x, const auto &y) {
if (y < x) {
x = y;
return 1;
}
return 0;
}
bool maxi(auto &x, const auto &y) {
if (y > x) {
x = y;
return 1;
}
return 0;
}
void run();
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
run();
return 0;
}
const ll MOD = (ll) 1e9 + 7;
ll power(ll x, ll y) {
if (y == 0) {
return 1;
}
if (y % 2 == 0) {
ll t = power(x, y / 2);
return t * t % MOD;
} else {
return power(x, y - 1) * x % MOD;
}
}
const int N = 3003;
int H, W;
ll g[N];
ll f[N][N];
ll fact[N], rfact[N];
ll cnk(int n, int k) {
if (k > n) {
return 0;
}
return fact[n] * rfact[n - k] % MOD * rfact[k] % MOD;
}
ll dp[N][N];
ll get(int w, int h) {
if (w < 0 || h < 0) {
return 0;
}
return dp[w][h];
}
void run() {
fact[0] = 1;
rep(i, 1, N) {
fact[i] = fact[i - 1] * i % MOD;
}
rep(i, 0, N) {
rfact[i] = power(fact[i], MOD - 2);
}
dp[0][0] = 1;
rep(w, 1, N) {
rep(h, 1, N) {
ll res = get(w - 2, h - 1) * cnk(w, 2) % MOD;
res = (res + 4 * w * get(w - 1, h - 1) % MOD) % MOD;
res = (res + w * (h - 1) * get(w - 1, h - 2) % MOD) % MOD;
dp[w][h] = res;
}
}
ll ans = 0;
cin >> H >> W;
rep(h, 1, H + 1) {
rep(w, 1, W + 1) {
ans = (ans + get(w, h) * cnk(W, w) % MOD * cnk(H, h) % MOD) % MOD;
}
}
cout << ans << "\n";
}
