import sys input = sys.stdin.readline N=int(input()) L=list(map(int,input().split())) K=int(input()) OK=max(L)/K NG=sum(L)/K while NG-OK>=max(10**(-9),OK/(10**9)): mid=(OK+NG)/2 ST=0 for l in L: ST+=l//mid if ST>=K: break if ST>=K: OK=mid else: NG=mid print(OK)