n=int(input()) al=list(map(int,input().split())) k=int(input()) def zen(x): ans=0 for i in al: if i>=x:ans+=i//x return ans ok,ng=0,10**10+1 while(ng-ok>=10**-12): mid=(ok+ng)/2 if zen(mid)>=k:ok=mid else:ng=mid print(ok)