n=input()
la=map(int,raw_input().split())
k=input()

eps=1e-9
l=0.0
r=1e9

while all([d>eps for d in [abs(l-r),abs(l-r)/r]]):
    c=(l+r)/2
    if sum([i//c for i in la])>=k:
        l=c
    else:
        r=c

print (l+r)/2