import sys input=lambda:sys.stdin.readline().rstrip() N=int(input()) L=list(map(int,input().split())) K=int(input()) m=[0.0,float(max(L))] while m[1]-m[0]>10**(-10): mid=sum(m)/2 count=0 for i in L: count+=int(i/mid) m[K>count]=mid print(m[1])