#include <bits/stdc++.h>
#define lsb(x) (x & (-x))
#define ll long long
#define ull unsigned long long
// 217
// 44
using namespace std;
const int MOD = (int) 1e9 + 7;
inline int lgput(int a, int b) {
int ans = 1;
while(b > 0) {
if(b & 1) ans = (1LL * ans * a) % MOD;
b >>= 1;
a = (1LL * a * a) % MOD;
}
return ans;
}
inline void mod(int &x) {
if(x >= MOD) x -= MOD;
}
inline void add(int &x, int y) {
x += y;
mod(x);
}
vector <int> fact, invfact;
inline void prec(int n) {
fact.resize(n + 1), invfact.resize(n + 1);
fact[0] = 1;
for(int i = 1; i <= n; i++) {
fact[i] = (1LL * fact[i - 1] * i) % MOD;
}
for(int i = 0; i <= n; i++) {
invfact[i] = lgput(fact[i], MOD - 2);
}
}
inline int comb(int n, int k) {
if(n < k) return 0;
return (1LL * fact[n] * (1LL * invfact[k] * invfact[n - k] % MOD)) % MOD;
}
int main() {
//ifstream cin("A.in");
//ofstream cout("A.out");
int i, j, n, m;
ios::sync_with_stdio(false);
cin.tie(0), cout.tie(0);
cin >> n >> m;
prec(n + m);
vector < vector <int> > dp(n + 1, vector <int>(m + 1));
for(i = 0; i <= n; i++) {
dp[i][0] = 1;
}
for(i = 0; i <= m; i++) {
dp[0][i] = 1;
}
for(i = 1; i <= n; i++) {
for(j = 1; j <= m; j++) {
dp[i][j] = dp[i - 1][j];
dp[i][j] = (dp[i][j] + 4LL * j * dp[i - 1][j - 1]) % MOD;
if(j >= 2) {
dp[i][j] = (dp[i][j] + 1LL * comb(j, 2) * dp[i - 1][j - 2]) % MOD;
}
if(i >= 2) {
dp[i][j] = (dp[i][j] + 1LL * j * (i - 1) * dp[i - 2][j - 1]) % MOD;
}
}
}
dp[n][m] += MOD - 1;
mod(dp[n][m]);
cout << dp[n][m];
//cin.close();
//cout.close();
return 0;
}
