#include<cstdio>
const long long mod = 1e9+7;
long long f[200005];
long long cc[200005];
long long a[200005];
long long sum[200005];

long long power(long long a,long long b){
    long long res = 1;
    while(b){
        if(b&1) res = res*a%mod;
        a = a*a%mod;
        b /= 2;
    }
    return res;
}

long long inv(long long u){ return power(u,mod-2); }

long long getComb(int n,int m){
    if(m>n || m<0) return 0;
    else{
        long long res = f[n]*inv(f[n-m])%mod*inv(f[m])%mod;
        return res;
    }
}

void preWork(long long k,long long n){
    f[0] = 1;
    for(int i = 1; i <= n; i++){
        f[i] = f[i-1]*(long long)i%mod;
    }
    long long fac = 1;
    for(long long i = k-1; i >= k; i--) fac = fac*i%mod;
    cc[0] = fac; 
    for(long long i = 1; i <= n; i++){
        fac = fac*(long long)(k+i-1)%mod;
        cc[i] = fac*inv(f[i])%mod;
    }
    sum[0] = cc[0];
    for(int i = 1; i <= n; i++){
        sum[i] = (sum[i-1]+cc[i])%mod;
    }
}
/*
5 100000000
cc[0] = 1
cc[1] = 100000000
cc[2] = 15000000
cc[3] = 6500000
cc[4] = 3737500
cc[5] = 2466750
*/

int main(){
    int n,k;
    scanf("%d%d",&n,&k);
    preWork(k,n);
    long long ans = 0;
    for(int i = 1; i <= n; i++){ 
        long long u;
        scanf("%lld",&u);
        long long cnt = sum[i-1]*sum[n-i]%mod;
        if(k==0) cnt = 1;
        ans += u*cnt%mod;
        if(ans>=mod) ans -= mod;
    }
    printf("%lld\n",ans);
    return 0;
}