#include<stdio.h>
int main(){
  int n,m,p,x[1000],i,sum;
  while(1){
    sum=0;
    scanf("%d%d%d",&n,&m,&p);
    if((n==0)&&(m==0)&&(p==0))
      break;
    for(i=0;i<n;i++){
      scanf("%d",&x[i]);
      sum=sum+x[i];
    }
    printf("%d\n",(sum*p)/x[m-1]);
  }
  return 0;
}