#include<bits/stdc++.h>

 using namespace std;

 typedef long long ll;

 ll read(){

     ll x=,f=;char c=getchar();

     while(c<'' || c>''){if(c=='-')f=-;c=getchar();}

     while(c>='' && c<=''){x=x*+c-'';c=getchar();}

     return x*f;

 }

 const ll mod=1000000007ll;

 ll n;

 int k;

 ll mat[][];

 ll calc(ll a,ll b){

     ll ret=;

     for(int i=;i<=b;i++)

         ret=ret*(a-i+)/i;

     return ret%mod;

 }

 ll ksm(ll a,ll b){

     if(b==) return ;

     ll nw=;

     if(b==) return a%mod;

     if(b&) nw=a;

     ll ret=ksm(a,b/);

     return ret*(nw%mod)%mod*ret%mod;

 }

 inline ll pd(ll x){

     if(x&) return -;

     return ;

 }

 ll ans[];

 int main(){

     #ifdef LZT

     //freopen("in","r",stdin);

     #endif

     n=read(),k=read();

     for(int i=;i<=k;i++){

         mat[i][]=calc(k,i)*pd(i+);

         mat[i][i]--;

         int st=i-;

         for(int j=;j<=i;j++)

             mat[i][j]+=(*calc(k-j,st)*pd(st--));

     }

     for(int i=;i<=k;i++){

         ll nw=;

         for(int j=;j<i;j++) nw=nw+mat[i][j]*ans[j];

         ans[i]=(mat[i][]-nw)/mat[i][i];

     }

     for(int i=;i<=k;i++)

         ans[i]=ans[i]%mod;

     ll res=ans[k]*ksm(,n)%mod;

     for(int i=;i<=k;i++){

         ll nw=ans[i]*ksm(n,k-i)%mod;

         res=(res-nw+mod)%mod;

     }

     printf("%lld\n",res);

     return ;

 }