#include<bits/stdc++.h>
using namespace std;
void DBG() { cerr << "]\n"; }
template<class H, class... T> void DBG(H h, T... t) {
cerr << h; if(sizeof...(t)) cerr << ", ";
DBG(t...);
}
#ifdef LOCAL
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define dbg(...) 0
#endif // LOCAL
#define FOR(i,a,b) for(int i = (a) ; i<(b) ; i++)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for(int i = (b)-1 ; i>=(a) ; i--)
#define R0F(i,a) ROF(i,0,a)
#define each(e,a) for(auto &e : (a))
#define sz(v) (int)(v).size()
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define pb push_back
#define tcT template<class T
#define nl "\n"
using ll = long long;
using vi = vector<int>;
using pi = pair<int,int>;
using str = string;
tcT> using V = vector<T>;
tcT> using pqg = priority_queue<T,vector<T>,greater<T>>;
void setIO(string NAME = "") {
cin.tie(0)->sync_with_stdio(0);
if(sz(NAME)) {
freopen((NAME + ".inp").c_str(),"r",stdin);
freopen((NAME + ".out").c_str(),"w",stdout);
}
}
const int MOD = 1e9 + 7;
const int MX = 3005;
ll dp[MX][MX];
int H, W;
int add(int a, int b) {
if((a += b) >= MOD) a-=MOD;
return a;
}
ll mul(ll a, ll b) {
return 1LL*a*b%MOD;
}
ll calc(int h, int w) {
if(h <= 0 || w <= 0) return 1;
if(~dp[h][w]) return dp[h][w];
ll &res = dp[h][w];
res = 0;
res = add(res, calc(h-1, w));
res = add(res, mul(4, mul(w, calc(h-1, w-1))));
res = add(res, mul(1LL*w*(w-1)/2, calc(h-1, w-2)));
res = add(res, mul(1LL*w*(h-1), calc(h-2, w-1)));
return res;
}
void solve() {
memset(dp, -1, sizeof dp);
cin>>H>>W;
cout << add(calc(H, W), MOD-1) << nl;
}
int main() {
setIO();
int t=1;
//cin>>t;
while(t-->0) {
solve();
}
return 0;
}
