#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
#define maxn 3300
int n, k, dp[maxn][maxn];
int mod = 1e9+7;
void solve() {
cin >> n >> k;
//dp[i][j] = ja colocou ate o i e esta ocupando j dias
dp[1][1] = 1;
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= k; j++) {
// cout << i << " " << j << " " << dp[i][j] << endl;
dp[i][j]%= mod;
dp[i+1][j]+= dp[i][j]*j;
// cout << i << " " << j << " -> " << i+1 << " " << j << " -=- " << dp[i][j] << endl;
dp[i+1][j+1]+= dp[i][j]*(i+1-j);
// cout << i << " " << j << " -> " << i+1 << " " << j+1 << " -=- " << dp[i][j]*i << endl;
}
}
cout << dp[n][k]<< endl;
}
int32_t main() {
ios::sync_with_stdio(false); cin.tie(0);
// freopen("in.in", "r", stdin);
//freopen("out.out", "w", stdout);
int tt = 1;
// cin >> tt;
while(tt--) solve();
}
