#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int MXN = 3003;
const ll  MOD = 1e9+7;
int n, k;
ll dp[MXN][MXN];
int32_t main() {
    cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
    cin >> n >> k;
    for(int i=1; i<=n; i++) dp[i][1] = 1;
    for(int i=2; i<=n; i++)
        for(int j=2; j<=i; j++)
            dp[i][j] = ((i-j+1)*dp[i-1][j-1] + j*dp[i-1][j]) % MOD;
    cout << dp[n][k] << '\n';
}
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