// Om Namah Shivaya
#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;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a, b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a, b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
/*
refs:
https://codeforces.com/blog/entry/58433?#comment-421099
no row/col has > 2 points
key idea:
order the points in some way
increasing coordinate of column (j value)
*/
const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
void solve(int test_case)
{
ll n,m; cin >> n >> m;
ll dp[n+5][m+5];
memset(dp,0,sizeof dp);
rep(i,n+1){
dp[i][0] = 1;
}
rep(j,m+1){
dp[0][j] = 1;
}
rep1(i,n){
rep1(j,m){
// place nothing on curr col
dp[i][j] += dp[i][j-1];
// place individual guy on curr col
dp[i][j] += i*4*dp[i-1][j-1];
// place pair on curr col
dp[i][j] += (i*(i-1)/2) * dp[i-2][j-1];
// place pair on same row, but one of the points must be in curr col
// i ways to pick row
// first point is in col j
// j-1 ways to pick col of other point
dp[i][j] += i*(j-1) * dp[i-1][j-2];
dp[i][j] %= MOD;
}
}
// sub 1 for empty case
ll ans = (dp[n][m]-1+MOD) % MOD;
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
