/*
 * FileName:     code
 * CreatedDate:  2020-08-19 16:15:34 +0900
 * LastModified: 2020-08-19 16:40:02 +0900
 */

#include <stdio.h>
#include <stdlib.h>
#define l_max 1e9
#define error 1e-9

int C(double *L, int N, long int K, double middle){
    long int num = 0;
    for(int i=0; i<N; i++){
        num += (long int)(L[i]/middle);
    }
    if(K>num){
        return 1;
    }
    else{
        return 0;
    }
}


int main(void){
    int N;scanf("%d", &N);
    double *L = malloc(N*sizeof(double));
    for(int i=0; i<N; i++)scanf("%lf", L+i);
    long int K;scanf("%ld", &K);
    double left = 0, right = l_max, middle;
    for(int i=0; i<100; i++){
//        double left = 0, right = l_max;
        middle = (left + right)/2;
        if(C(L, N, K, middle)){
            right = middle;
        }
        else{
            left = middle;
        }
    }
    printf("%lf\n", middle);
    return 0;
}