n=int(input())
ls=list(map(int,input().split()))
k=int(input())
low=0
high=max(ls)
for i in range(61):
    mid= (high+low)/2
    ct=0
    for l in ls:
        ct+=l//mid 
    if ct>=k:
        low=mid 
    else:
        high=mid
print('{:.20f}'.format(mid))