#include "bits/stdc++.h"
using namespace std;
#ifdef DEBUG
auto&operator<<(auto &o, pair<auto, auto> p) {o << "(" << p.first << ", " << p.second << ")"; return o;}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{"; for(auto e : x) o<<e<<", "; return o<<"}";}
#define debug(X) cerr << "["#X"]: " << X << '\n';
#else
#define cerr if(0)cout
#define debug(X) ;
#endif
using ll = long long;
#define all(v) (v).begin(), (v).end()
#define ssize(x) int(x.size())
#define fi first
#define se second
#define mp make_pair
#define eb emplace_back
const int mod = 1'000'000'007;
int add(int a, int b) {
a += b;
return a >= mod ? a-mod : a;
}
int sub(int a, int b) {
return add(a, mod-b);
}
int mul(int a, int b) {
return int(((ll)a*b)%mod);
}
int fpow(int a, int b) {
int res = 1;
while (b) {
if (b&1) {
res = mul(a, res);
b--;
}
a = mul(a, a);
b /= 2;
}
return res;
}
int inv(int x) {
return fpow(x, mod-2);
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int n, m;
cin >> n >> m;
vector<vector<int>> dp(n+1, vector<int>(m+1, 1));
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
dp[i][j] = 0;
if (i-2 >= 0 && j-1 >= 0) dp[i][j] = add(dp[i][j],
mul(mul(i, mul(i-1, inv(2))), dp[i-2][j-1]));
if (i-1 >= 0 && j-2 >= 0) dp[i][j] = add(dp[i][j],
mul(i, mul(j-1, dp[i-1][j-2])));
dp[i][j] = add(dp[i][j], mul(4*i, dp[i-1][j-1]));
dp[i][j] = add(dp[i][j], dp[i][j-1]);
}
}
debug(dp);
cout << sub(dp[n][m], 1) << '\n';
return 0;
}
