#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;
#define fbo find_by_order
#define ook order_of_key
#define f first
#define s second
#define pb push_back
#define reset(a,b) memset(a,b,sizeof a);
#define MOD 1000000007
#define MID (l+r)/2
#define ALL(x) x.begin(),x.end()
#define debug(x) cout<<#x<<" = "<<(x)<<endl
#define mx 3003
#define pc(x) putchar_unlocked(x);
typedef tree<long long, null_type, less<long long>, rb_tree_tag, tree_order_statistics_node_update> pbds;
long long dep[mx][mx],n,k;
long long dp(int n,int k){
if(k>=n)return 0;
if(k==0 || k==n-1)return 1;
long long&ret=dep[n][k];
if(ret!=-1)return ret;
ret=0;
ret=1LL*(n-k)*dp(n-1,k-1)%MOD+1LL*(k+1)*dp(n-1,k)%MOD;
ret%=MOD;
//cout<<n<<' '<<k<<' '<<ret<<endl;
return ret;
}
int main(){
reset(dep,-1);
cin>>n>>k;
cout<<dp(n,k-1)<<endl;
}
