N =int(input()) li =[int(i)for i in input().split()] K =int(input()) def wa(L,d): n = 0 for i in L: n += int(i/d) return n def nibuntansaku(l,s): left = max(l)+1 right =0 while abs(right -left) > 10**(-3): mid = (left + right)/2.0 if wa(l,mid) >= s: right =mid else: left =mid return right #s以上の値をとる最小のindexが返る print(nibuntansaku(li,K))