#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(x) (x).begin(), (x).end()
template<int MD> struct mi {
int v;
explicit operator int() const { return v; }
mi(long long _v = 0) {
v = (-MD <= _v && _v < MD) ? _v : _v % MD;
if (v < 0) v += MD;
}
mi &operator+=(const mi &o) { if ((v += o.v) >= MD) v -= MD; return *this; }
mi &operator-=(const mi &o) { if ((v -= o.v) < 0) v += MD; return *this; }
mi &operator*=(const mi &o) { v = 1LL * v * o.v % MD; return *this; }
mi &operator/=(const mi &o) { return (*this) *= inv(o); }
friend mi operator+(mi a, const mi &b) { return a += b; }
friend mi operator-(mi a, const mi &b) { return a -= b; }
friend mi operator*(mi a, const mi &b) { return a *= b; }
friend mi operator/(mi a, const mi &b) { return a /= b; }
friend mi inv(const mi &m) { return binpow(m, MD - 2); }
friend mi binpow(mi b, long long e) {
mi ret = 1;
for (; e; e >>= 1, b *= b) if (e & 1) ret *= b;
return ret;
}
friend bool operator==(const mi &a, const mi &b) { return a.v == b.v; }
friend bool operator!=(const mi &a, const mi &b) { return !(a == b); }
friend bool operator<(const mi &a, const mi &b) { return a.v < b.v; }
friend istream &operator>>(istream &i, mi &m) { long long x; i >> x; m.v = x; return i; }
friend ostream &operator<<(ostream &o, const mi &m) { o << m.v; return o; }
};
const int N = 3007, mod = 1e9 + 7;
using Mint = mi<mod>;
int n, m;
Mint fac[N], ifac[N];
Mint dp[N][N];
Mint nck(int n, int k) {
return fac[n] * ifac[n - k] * ifac[k];
}
int main() {
cin.tie(0)->sync_with_stdio(false);
fac[0] = 1;
for (int i = 1; i < N; i++)
fac[i] = fac[i - 1] * i;
ifac[N - 1] = binpow(fac[N - 1], mod - 2);
for (int i = N - 2; ~i; i--)
ifac[i] = ifac[i + 1] * (i + 1);
cin >> n >> m;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= m; j++) {
if (i == 0 || j == 0)
dp[i][j] = 1;
else
dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1] * j * 4;
}
}
Mint ans = 0;
for (int i = 0; i <= min(n / 2, m); i++) {
Mint w = nck(m, i) * nck(n, i * 2) * fac[i * 2] / binpow((Mint) 2, i);
int nn = n - i * 2, nm = m - i;
for (int j = 0; j <= min(nm / 2, nn); j++) {
Mint cur = w * nck(nn, j) * nck(nm, j * 2) * fac[j * 2] / binpow((Mint) 2, j);
ans += cur * dp[nn - j][nm - j * 2];
}
}
cout << ans - 1 << '\n';
return 0;
}
