#include "stdio.h"
#include "string.h"

int main()
{   long c[10001]={'\0'};
    char s[10]={'\0'};
    int m;
    long a, average, b, i, k, j;
    long long sum=0, x[9]={1,10,100,1000,10000,100000,1000000,10000000,100000000};
    scanf("%ld %ld",&a,&b);
    for ( i=0; i<a; i++)
    {
        scanf("%s",s);
        m=strlen(s);
        for( j=0,k=m-2; j<m; j++)
           if(s[j]!='.') c[i] += (s[j]-'0')*x[k--];
        sum += c[i];
    }
    average = sum/b;
    for ( i=average; i>0; i--)
    {   k=0;
        for ( j=0; j<a; j++)
        {
            k += c[j]/i;
        }
        if( k>=b ) break;
    }
    printf("%.2f\n",i/100.0);
    return 0;
}