#include<bits/stdc++.h>
using namespace std;
/*
Numero de permutacoes de tamanho n com k-1 descidas
n = 3, k = 2:
1) 1 3 2 [1, 3], [2]
2) 2 1 3 [2], [1, 3]
3) 2 3 1 [2, 3], [1]
4) 3 1 2 [3], [1, 2]
*/
typedef long long ll;
const int maxn = 3010, mod = 1e9 + 7;
int dp[maxn][maxn];
int solve(int n, int k){
if(n == 1) return k == 1;
if(dp[n][k] != -1) return dp[n][k];
ll tot = 1LL * solve(n-1, k) * k + 1LL * solve(n-1, k-1) * (n - k + 1);
tot %= mod;
return dp[n][k] = tot;
}
int main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
int n, k;
cin >> n >> k;
memset(dp, -1, sizeof dp);
cout << solve(n, k);
return 0;
}
