#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
using namespace std;
const int64_t MOD=1e9+7;
const int64_t N=3005;
int64_t h,w;
int64_t fac[N];
int64_t ifac[N];
int64_t pow2[N];
int64_t ipow2[N];
int64_t dp[N][N];
int64_t binexp(int64_t n, int64_t k){
int ans=1;
while(k>0){
if(k%2==1){
ans=(ans*n)%MOD;
}
n=(n*n)%MOD;
k/=2;
}
return ans;
}
int64_t inv(int64_t n){
return binexp(n,MOD-2);
}
int64_t c(int64_t n, int64_t k){
return (((fac[n]*ifac[k])%MOD)*ifac[k-1])%MOD;
}
int64_t fdp(int64_t n, int64_t m){
if(dp[n][m])return dp[n][m];
if(n<=0||m<=0)return 1;
//no tent in row
int64_t ans=fdp(n-1,m);
//place one tent in row (m column choice)
ans=(ans+fdp(n-1,m-1)*4*m)%MOD;
//place two tents in column (one in cur row) (m columns, then n-1 free rows)
ans=(ans+fdp(n-2,m-1)*m*(n-1))%MOD;
//place two tents in row (one in cur column) (m columns, then m-1 free columns) (dependent so we divide by two)
ans=(ans+fdp(n-1,m-2)*m*(m-1)/2)%MOD;
dp[n][m]=ans;
return ans;
}
void solve() {
cin>>h>>w;
fac[0]=1;
pow2[0]=1;
for(int i=1;i<N;i++){
fac[i]=(fac[i-1]*i)%MOD;
pow2[i]=(pow2[i-1]*2)%MOD;
}
ifac[N-1]=inv(fac[N-1]);
ipow2[N-1]=inv(pow2[N-1]);
for(int i=N-2;i>=0;i--){
ifac[i]=(ifac[i+1]*(i+1))%MOD;
ipow2[i]=(ipow2[i+1]*2)%MOD;
}
int64_t ans=(fdp(h,w)-1)%MOD;
cout<<ans<<'\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int64_t t=1;
//cin>>t;
while(t--){
solve();
}
return 0;
}
