#include "bits/stdc++.h"
using namespace std;
#define for_(i, s, e) for (int i = s; i < (int) e; i++)
#define for__(i, s, e) for (ll i = s; i < e; i++)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
#define endl '\n'
const ll mod = 1e9+7;
ll ncr(ll n, ll r) {
if (r == 0) return 1;
if (r == 1) return n;
if (r == 2) return ((n*(n-1))/2 % mod);
assert(false);
}
int main() {
#ifdef mlocal
freopen("test.in", "r", stdin);
#endif
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m; cin >> n >> m;
ll dp[n+1][m+1]; // [row][empty][light]
memset(dp, 0, sizeof(dp));
vector<ll> tp(m+1);
tp[0] = 1;
for_(i, 1, tp.size()) tp[i] = (4*tp[i-1]) % mod;
for_(i, 0, m+1) dp[n][i] = 1;
for (int i = n-1; i >= 0; i--) {
for_(emp, 0, m+1) {
dp[i][emp] = dp[i+1][emp];
if (emp >= 2) {
dp[i][emp] += ((dp[i+1][emp-2] * ncr(emp, 2)) % mod);
if (dp[i][emp] >= mod) dp[i][emp] -= mod;
}
if (emp >= 1) {
if (i < n-1) dp[i][emp] += (emp * (n-i-1) * dp[i+2][emp-1]) % mod;
if (dp[i][emp] >= mod) dp[i][emp] -= mod;
dp[i][emp] += (((dp[i+1][emp-1] * 4) % mod) * emp) % mod;
if (dp[i][emp] >= mod) dp[i][emp] -= mod;
}
}
}
cout << (dp[0][m]-1+mod) % mod << endl;
return 0;
}
