#pragma GCC optimize("Ofast,unroll-loops")
// #pragma comment(linker, "/stack:200000000")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma,tune=native")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef int ll;
typedef long double ld;
typedef pair <ll, ll> pll;
#ifdef SINA
#define dbg(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << std::endl; }
template <typename Arg1, typename... Args> void __f (const char* names, Arg1&& arg1, Args&&... args) {
const char* comma = strchr(names + 1, ',');cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...); }
#define dbg2(x, j, n) cout<< #x << " : "; output((j), (n), x, 1); cout.flush();
#else
#define dbg(...) 0
#define dbg2(x, j, n) 0
#endif
#define SZ(x) ((ll)((x).size()))
#define File(s, t) freopen(s ".txt", "r", stdin); freopen(t ".txt", "w", stdout);
#define input(j, n, a) for (int _i = (j); _i < (n)+(j); _i++) cin>> a[_i];
#define output(j, n, a, t) for (int _i = (j); _i < (n)+(j); _i++) cout<< a[_i] << (((t) && _i != (n)+(j)-1)? ' ' : '\n');
#define kill(x) return cout<< x << endl, 0
#define cl const ll
#define fr first
#define sc second
#define lc (v << 1)
#define rc (lc | 1)
#define mid ((l + r) >> 1)
#define All(x) (x).begin(), (x).end()
cl inf = sizeof(ll) == 4 ? (1e9 + 10) : (3e18), mod = 1e9 + 7, MOD = 998244353;
template <class A, class B> ostream& operator << (ostream& out, const pair<A, B> &a) {
return out << '(' << a.first << ", " << a.second << ')'; }
template <class A> ostream& operator << (ostream& out, const vector<A> &a) {
if(a.empty())return out<<"[]";out<< '[' << a[0]; for (int i = 0; ++i < (int)(a.size());)out<< ", " <<a[i];return out<<']';}
template <class T, typename _t = less <T> > using Tree = tree <T, null_type, _t, rb_tree_tag, tree_order_statistics_node_update>;
#define C2(x) (1LL * (x) * ((x) - 1) / 2)
cl N = 3e3 + 3;
ll dp [N][N], n, m;
int main ()
{
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
for (ll i = 0; i < N; i++) for (ll j = 0; j < N; j++) dp[i][j] = 1;
cin>> n >> m;
for (ll i = 1; i <= n; i++) for (ll j = 1; j <= m; j++) {
dp[i][j] = dp[i - 1][j];
(dp[i][j] += 4LL * j * dp[i - 1][j - 1] % mod) %= mod;
(dp[i][j] += C2(j) * dp[i - 1][j - 2] % mod) %= mod;
(dp[i][j] += 1LL * j * (i - 1) * dp[i - 2][j - 1] % mod) %= mod;
}
cout<< (dp[n][m] - 1 + mod) % mod << endl;
return 0;
}
/*
*/
