from functools import reduce
from fractions import gcd
import math
import bisect
import itertools
import sys
sys.setrecursionlimit(10**7)
input = sys.stdin.readline
INF = float("inf")


def main():
    def isOK(m):
        k = 0
        for l in L:
            k += l//m
        return k >= K


    def binary_search(ok, ng):
        while abs(ok - ng) > 10**(-9):
            mid = (ok + ng) / 2
            if isOK(mid):
                ok = mid
            else:
                ng = mid
        return ok    


    N = int(input())
    L = list(map(int, input().split()))
    K = int(input())

    ok = 0
    ng = 10**9 + 1

    print(binary_search(ok, ng))


if __name__ == '__main__':
    main()