#include<bits/stdc++.h>
using namespace std;
#define VA_NUM_ARGS(...) VA_NUM_ARGS_IMPL_((0,__VA_ARGS__, 6,5,4,3,2,1))
#define VA_NUM_ARGS_IMPL_(tuple) VA_NUM_ARGS_IMPL tuple
#define VA_NUM_ARGS_IMPL(_0,_1,_2,_3,_4,_5,_6,N,...) N
#define macro_dispatcher(macro, ...) macro_dispatcher_(macro, VA_NUM_ARGS(__VA_ARGS__))
#define macro_dispatcher_(macro, nargs) macro_dispatcher__(macro, nargs)
#define macro_dispatcher__(macro, nargs) macro_dispatcher___(macro, nargs)
#define macro_dispatcher___(macro, nargs) macro ## nargs
#define Debug1(a) cout<<#a<<"="<<(a)<<"\n"
#define Debug2(a,b) cout<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<"\n"
#define Debug3(a,b,c) cout<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<", "<<#c<<"="<<(c)<<"\n"
#define Debug4(a,b,c,d) cout<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<", "<<#c<<"="<<(c)<<", "<<#d<<"="<<(d)<<"\n"
#define Debug5(a,b,c,d,e) cout<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<", "<<#c<<"="<<(c)<<", "<<#d<<"="<<(d)<<", "<<#e<<"="<<(e)<<"\n"
#define Debug6(a,b,c,d,e,f) cout<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<", "<<#c<<"="<<(c)<<", "<<#d<<"="<<(d)<<", "<<#e<<"="<<(e)<<", "<<#f<<"="<<(f)<<"\n"
#define Debug(...) macro_dispatcher(Debug, __VA_ARGS__)(__VA_ARGS__)
#define DA(a,n) cout<<#a<<"=["; printarray(a,n); cout<<"]\n"
#define DAR(a,n,s) cout<<#a<<"["<<s<<"-"<<n-1<<"]=["; printarray(a,n,s); cout<<"]\n"
#define TT1 template<class T>
#define TT1T2 template<class T1, class T2>
#define TT1T2T3 template<class T1, class T2, class T3>
template<class T, size_t N> ostream& operator << (ostream& os, const array<T, N>& v);
TT1T2 ostream& operator << (ostream& os, const pair<T1, T2>& p){ return os <<"("<<p.first<<", "<< p.second<<")"; }
TT1 ostream& operator << (ostream& os, const vector<T>& v){ bool f=1;os<<"[";for(auto& i : v) { if (!f)os << ", ";os<<i;f=0;}return os << "]"; }
template<class T, size_t N> ostream& operator << (ostream& os, const array<T, N>& v) { bool f=1;os<<"[";for(auto& i : v) { if (!f)os << ", ";os<<i;f=0;}return os << "]"; }
TT1T2 ostream& operator << (ostream& os, const set<T1, T2>&v){ bool f=1;os<<"[";for(auto& i : v) { if (!f)os << ", ";os<<i;f=0;}return os << "]"; }
TT1T2 ostream& operator << (ostream& os, const multiset<T1,T2>&v){bool f=1;os<<"[";for(auto& i : v) { if (!f)os << ", ";os<<i;f=0;}return os << "]"; }
TT1T2T3 ostream& operator << (ostream& os, const map<T1,T2,T3>& v){ bool f = 1; os << "["; for (auto& ii : v) { if (!f)os << ", "; os << "(" << ii.first << " -> " << ii.second << ") "; f = 0; }return os << "]"; }
TT1T2 ostream& operator << (ostream& os, const multimap<T1, T2>& v){ bool f = 1; os << "["; for (auto& ii : v) { if (!f)os << ", "; os << "(" << ii.first << " -> " << ii.second << ") "; f = 0; }return os << "]"; }
TT1T2 ostream& operator << (ostream& os, priority_queue<T1, T2> v) { bool f = 1; os << "["; while (!v.empty()) { auto x = v.top(); v.pop(); if (!f) os << ", "; f = 0; os << x; } return os << "]"; }
TT1T2 void printarray(const T1& a, T2 sz, T2 beg = 0){ for (T2 i = beg; i<sz; i++) cout << a[i] << " "; cout << endl; }
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> Pi;
typedef pair<ll, ll> Pll;
#define Fi first
#define Se second
#define pb(x) push_back(x)
#define sz(x) (int)x.size()
#define rep(i, n) for(int i=0;i<n;i++)
#define repp(i, n) for(int i=1;i<=n;i++)
#define all(x) x.begin(), x.end()
#define geti1(X) cin >> X
#define geti2(X,Y) cin >> X >> Y
#define geti3(X,Y,Z) cin >> X >> Y >> Z
#define geti4(X,Y,Z,W) cin >> X >> Y >> Z >> W
#define GET_MACRO(_1,_2,_3,_4,NAME,...) NAME
#define geti(...) GET_MACRO(__VA_ARGS__, geti4, geti3, geti2, geti1) (__VA_ARGS__)
#define INF 987654321
#define endl '\n'
const ll mod = 1e9 + 7;
ll cdp[5000][5000], dp[5050][5050];
ll odd[6000], even[6000];
ll fpow(ll a, ll b){
ll res = 1, t = a;
while( b ){
if( b&1 ) res = (res*t)%mod;
t = (t*t)%mod;
b >>= 1;
}
return res;
}
ll inv(ll x){
return fpow(x,mod-2);
}
ll C(int n, int m){
if( n == m || m == 0 ) return 1;
ll& res = cdp[n][m];
if( res != -1 ) return res;
res = C(n-1,m) + C(n-1,m-1);
res %= mod;
return res;
}
int N,M;
int main(){
memset(cdp,-1,sizeof cdp);
geti(N,M);
even[0] = 1; even[1] = 1;
odd[0] = 1; odd[1] = 1;
for(int i=2;i<=5000;i++) {
if( i%2 == 0 ) even[i] = (even[i-1] * C(i,2)) % mod;
else even[i] = even[i-1];
if( i%2 == 1 ) odd[i] = (odd[i-1] * C(i,2)) %mod;
else odd[i] = odd[i-1];
}
for(int i=0;i<=5000;i++) dp[0][i] = dp[i][0] = 1;
for(int i=1;i<=N;i++){
for(int j=1;j<=M;j++){
dp[i][j] = dp[i-1][j];
ll tmp = (4 * j) % mod;
tmp = (tmp * dp[i-1][j-1]) % mod;
dp[i][j] = (dp[i][j] + tmp) % mod;
}
}
ll ans = 0;
for(ll a=0;a<=N;a++) for(ll b=0;b<=M;b++){
if( N-a-2*b < 0 || M-b-2*a < 0 ) continue;
ll tmp = ( C(N,a) * C(M,b) ) % mod;
if( (M-b)%2 == 0 ){
tmp = ( tmp * even[M-b] ) % mod;
tmp = ( tmp * inv(even[M-b-2*a]) ) % mod;
}
else{
tmp = ( tmp * odd[M-b] ) % mod;
tmp = ( tmp * inv(odd[M-b-2*a]) ) % mod;
}
if( (N-a)%2 == 0 ){
tmp = ( tmp * even[N-a] ) % mod;
tmp = ( tmp * inv(even[N-a-2*b]) ) % mod;
}
else{
tmp = ( tmp * odd[N-a] ) % mod;
tmp = ( tmp * inv(odd[N-a-2*b]) ) % mod;
}
//for(int x = M-b; x >= M-b-2*(a-1); x-=2) tmp = ( tmp * C(x,2) ) % mod;
//for(int x = N-a; x >= N-a-2*(b-1); x-=2) tmp = ( tmp * C(x,2) ) % mod;
tmp = (tmp * dp[N-a-2*b][M-b-2*a]) % mod;
ans = ( ans + tmp ) % mod;
}
ans = (ans - 1 + mod) % mod;
cout << ans << endl;
}
