class Solve:
    def __init__(self):
        self.N = int(input())
        self.L = [int(i) for i in input().split()]
        self.K = int(input())

        self.l = max([l/self.K for l in self.L])  # > 10**-10
        self.r = min(max(self.L)+1, sum(self.L)/self.K+1)  # < 10**9

    def check(self, l):
        k = 0
        for s in (s for s in self.L if s >= l):
            k += s // l
            if k >= self.K:
                return True
        return False

    def solve(self):
        for i in range(60):  # (10**9 - 10**-10) * 0.5**60 < 10**-9
            m = (self.l + self.r) / 2
            if self.check(m):
                self.l = m
            else:
                self.r = m
        return self.l

print(Solve().solve())