#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << " " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << " " << j << " " << #i << " " << q << " " << #p << endl;
#define show4(x,y) for(auto it:y) cout << it << " "; cout << #x << endl;
typedef pair<long long,long long>pii;
typedef pair<int,pii>pi2;
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
int n,k;
int memo[3005][3005];
const int mod=1e9+7;
int dp(int index, int day){
if(index==n+1){
if(day==k) return 1;
else return 0;
}
if(memo[index][day]!=-1) return memo[index][day];
int ans=0;
ans=(ans+dp(index+1,day)*(day))%mod;
ans=(ans+dp(index+1,day+1)*(index-day))%mod;
//show3(index,index,day,day,ans,ans);
return memo[index][day]=ans;
}
void solve(){
cin >> n >> k;
memset(memo,-1,sizeof(memo));
cout << dp(1,0);
}
int32_t main(){
ios::sync_with_stdio(0);
cin.tie(0);
int t=1;
//freopen("in.txt","r",stdin);
//cin >> t;
while(t--){
solve();
}
}
