#include <stdlib.h>
#include <stdio.h>
#if 0
#define ep printf
#else
#define ep 0 || 
#endif

int n,k;
int cbl[10000];

int spocti(int d){
 int a,r;
 if(!d)return k+1;
 r=0;
 for(a=0;a<n;a++){
  r+=cbl[a]/d;
 }
 return r;
}

int main(void){
 int a,b,c,d,h,r;
 while(1){
  scanf("%d %d\n",&n,&k);
  if(n==0 && k==0)break;
  r=0;
  for(a=0;a<n;a++){
   scanf("%d.",&b);
   scanf("%d\n",&c);
   cbl[a]=b*100+c;
   r+=b*100+c;
  }
  d=0;h=r/k+1;
  while(d<h){
   b=(d+h)/2;
   c=spocti(b);
   ep("d==%d, h==%d, b==%d, c==%d\n",d,h,b,c);
   if(c<k)h=b;
   else d=b+1;
  }
  r=d-1;
  printf("%d.%d%d\n",r/100,(r%100)/10,r%10);
 }
 return 0;
}