/*
TASK:seq
LANG:C
*/
/*
  Name: Zadacha B1. Redici
  Copyright: aRaGaR
  Author: Radoslav Rachev
  Date: 21.04.07 12:16
  Description: NOI III
*/
#include <stdio.h>

int used[2002]={0};
int pas [16]={0};

int main ()
{
    int i,j,n,k,cnt,sum=0;
    
    scanf ("%d %d",&n,&k);
    pas[0]=1;
    for (i=1;i<=n;i++)
        for (j=k;j>0;j--)
            {
                pas[j]+=pas[j-1];
                if (pas[j]<0)
                    {
                        printf ("0\n");
                        return 0;
                    }
            }
    cnt=pas[k]/2+pas[k]%2;
    
    for (i=0;i<n;i++)
        {
            scanf ("%d",&j);
            sum+=j;
        }
    sum*=cnt;
    printf ("%d\n",sum);
    
    return 0;
}
