#pragma GCC optimize("O3", "unroll-loops") // "Ofast"
#pragma GCC target("avx2", "bmi", "bmi2", "lzcnt", "popcnt")
#include <bits/stdc++.h>
//#define int long long
#define vt vector
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define ff first
#define ss second
#define dbg(x) cerr << #x << " = " << x << '\n'
#define bit(x, i) ((x) >> (i) & 1)
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vvt = vt< vt<int> >;
const int N = 1e6 + 5, mod = 1e9 + 7, B = 500;
const ll inf = 1e18 + 7, LIM = (1ll << 60);
const double eps = 1e-6;
ll add (ll a, ll b) {
a += b;
if (a < 0) a += mod;
if (a >= mod) a -= mod;
return a;
}
ll mul (ll a, ll b) {
a *= b;
if (a >= mod) a %= mod;
return a;
}
ll bp (ll n, ll k) {
ll res = 1;
while (k) {
if (k & 1) res = mul(res, n);
n = mul(n, n);
k >>= 1;
}
return res;
}
int h, w;
ll dp[3005][3005];
void solve () {
cin >> h >> w;
dp[0][0] = 1;
for (int i = 0; i <= 3000; i++) dp[i][0] = dp[0][i] = 1;
ll inv2 = bp(2, mod - 2);
for (int i = 1; i <= h; i++) {
for (int j = 1; j <= w; j++) {
dp[i][j] = add(dp[i][j], mul(dp[i - 1][j - 1], mul(j, 4)));
dp[i][j] = add(dp[i][j], dp[i - 1][j]);
if (i >= 2) dp[i][j] = add(dp[i][j], mul(dp[i - 2][j - 1], mul(j, (i - 1))));
if (j >= 2) dp[i][j] = add(dp[i][j], mul(dp[i - 1][j - 2], mul(mul(j, (j - 1)), inv2)));
}
}
dp[h][w] = add(dp[h][w], -1);
cout << dp[h][w];
cout << '\n';
}
bool testcases = 0;
signed main() {
#ifdef ONLINE_JUDGE
freopen(".in", "r", stdin);
freopen(".out", "w", stdout);
#endif
cin.tie(0) -> sync_with_stdio(0);
int test = 1;
if (testcases) cin >> test;
for (int cs = 1; cs <= test; cs++) {
solve();
}
}
