#include <bits/stdc++.h>
using namespace std;
#define f1r(i, a, b) for (int i = a; i < b; ++i)
#define f0r(i, a) f1r(i, 0, a)
#define each(t, a) for (auto& t : a)
#define mp make_pair
#define f first
#define s second
#define pb push_back
#define eb emplace_back
#define sz(x) (int)(x).size()
#define all(x) begin(x), end(x)
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
template <class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template <class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
const int N = 3005;
const int P = 1e9 + 7;
int mpow(ll b, ll e) {
ll r = 1;
while (e) {
if (e & 1) {
r *= b;
r %= P;
}
b *= b;
b %= P;
e >>= 1;
}
return r;
}
int minv(ll b) { return mpow(b, P - 2); }
int add(int x, int y) { x += y; if (x >= P) x -= P; return x; }
int sub(int x, int y) { x -= y; if (x < 0) x += P; return x; }
int mult(int x, int y) { return 1LL * x * y % P; }
int madd(int&x, int y) { return x = add(x, y); }
int mmult(int& x, int y) { return x = mult(x, y); }
int msub(int& x, int y) { return x = sub(x, y); }
int fact[N], ifact[N];
int dp[N][N];
int C(int x, int y) {
if (x < y) return 0;
return mult(fact[x], mult(ifact[y], ifact[x - y]));
}
int solve(int n, int m) {
auto& res = dp[n][m];
if (res != -1) return res;
res = 1; // no more pairs
if (n == 0 || m == 0) {
return res;
}
{ // first thing isn't paired
madd(res, sub(solve(n - 1, m), 1));
}
if (m >= 2) { // first thing is double paired
madd(res, mult(C(m, 2), solve(n - 1, m - 2)));
}
if (n >= 2) { // first thing is double paired with same side
madd(res, mult(mult(n - 1, m), solve(n - 2, m - 1)));
}
return res;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
fact[0] = 1;
f1r(i, 1, N) fact[i] = mult(fact[i - 1], i);
ifact[N - 1] = minv(fact[N - 1]);
f0r(i, N) f0r(j, N) dp[i][j] = -1;
for (int i = N - 2; i >= 0; i--) ifact[i] = mult(ifact[i + 1], i + 1);
int n, m; cin >> n >> m;
int ans = 0;
f0r(i, min(m, n) + 1) { // number of singles
int res = mult(fact[i], mult(C(n, i), C(m, i)));
mmult(res, mpow(4, i));
int a = n - i;
int b = m - i;
madd(ans, mult(res, solve(a, b)));
}
msub(ans, 1);
cout << ans << '\n';
return 0;
}
/**
* each vertex has at most degree 2
* no path of length greater than 3
* 4^(number of single components)
*
*/
