//#pragma optimization_level 3
//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/detail/standard_policies.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordset;
*/
#define fr first
#define sc second
#define vec vector
#define pb push_back
#define pii pair<int, int>
#define forn(x,y) for(int x = 1 ; x <= (int)y ; ++x)
#define all(x) (x).begin(),(x).end()
#define fast cin.tie(0);cout.tie(0);cin.sync_with_stdio(0);cout.sync_with_stdio(0);
using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef complex<int> point;
const int nmax = 3005;
const ll linf = 1e18;
const ll mod = 1e9+7;
const int inf = INT_MAX;
ll n, m;
ll f[nmax][nmax];
ll rec( ll x , ll y){
if( x < 0 || y < 0) return 0;
if( x == 0 || y == 0) return 1;
if(f[x][y]) return f[x][y];
f[x][y] = rec(x-1,y) + rec(x-1,y-1)*4LL*y % mod + rec(x-1,y-2)*(y *(y-1) / 2LL) % mod + rec(x-2,y-1)*y*(x-1)%mod;
f[x][y] %= mod;
return f[x][y];
}
int main(){
//
fast;
cin >> n >> m;
cout << (rec(n,m)+ mod - 1) % mod <<'\n';
}
