#include<iostream> |
#include<algorithm> |
using namespace std; |
const int lenn=10000; |
const int lens=500; |
int n,s; |
int a[lenn]; |
int wait[lens]; |
int find() |
{ |
int minTime=wait[0]; |
int pos=0; |
for ( int i=1; i<s; i++ ) |
{ |
if ( minTime>wait[i] ) |
{ |
minTime=wait[i]; |
pos=i; |
} |
} |
return pos; |
} |
int main() |
{ |
while ( cin>>n>>s ) |
{ |
int i; |
for ( i=0; i<n; i++ ) |
{ |
cin>>a[i]; |
} |
sort ( a,a+n ); |
memset ( wait,0, sizeof ( wait ) ); |
double sum=0; |
for ( i=0; i<n; i++ ) |
{ |
int t=find(); |
wait[t]+=a[i]; |
sum+=wait[t]; |
} |
double res=sum/n; |
printf ( "%.2f\n" ,res ); |
} |
return 0; |
} |