// High above the clouds there is a rainbow...
#include<bits/stdc++.h>
#define F first
#define S second
#define PB push_back
#define sz(s) int((s).size())
#define bit(n,k) (((n)>>(k))&1)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const int maxn=1e5+10,mod=1e9+7;
const ll inf=1e18;
int dp[maxn],fac[maxn],ifac[maxn],dp2[maxn];
int Pow(int a,int b){
int ans=1;
for(;b;b>>=1,a=1ll*a*a %mod){
if(b&1) ans=1ll*ans*a %mod;
}
return ans;
}
int C(int n,int k){
return 1ll*fac[n] * ifac[k] %mod *ifac[n-k] %mod;
}
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);
fac[0]=1;
for(int i=1;i<maxn;i++)
fac[i]=1ll*i*fac[i-1] %mod;
ifac[maxn-1]=Pow(fac[maxn-1],mod-2);
for(int i=maxn-2;i>=0;i--)
ifac[i]=1ll*(i+1)*ifac[i+1] %mod;
int n,k;cin>>n>>k;
for(int i=1;i<=k;i++){
dp2[i]=1ll*Pow(i,n);
for(int j=1;j<i;j++)
dp2[i]=(dp2[i]-1ll*dp2[j]*C(i,j))%mod;
dp[i]=dp2[i];
for(int j=1;j<i;j++)
dp[i]=(dp[i]-1ll*dp[j]*C(n-j,i-j))%mod;
}
if(dp[k]<0) dp[k]+=mod;
return cout<<dp[k]<<endl,0;
}
// Deathly mistakes:
// * Read the problem curfully.
// * Check maxn.
// * Overflows.
