import sys
import math


def input(): return sys.stdin.readline().rstrip()


def main():
    int(input())  # N
    *L, = map(int, input().split())
    K = int(input())

    def yes(x):
        return sum(math.floor(le/x) for le in L) >= K

    ok = 0
    ng = max(L) + 1
    while abs(ok-ng) > 1e-12:
        mi = (ok+ng)/2
        if yes(mi):
            ok = mi
        else:
            ng = mi

    print((ok+ng)/2)


if __name__ == '__main__':
    main()