def c(x):
    if x==0: return True
    global L,K
    ret = 0
    for l in L:
        ret += l//x
    return ret>=K

N = int(input())
L = list(map(int, input().split()))
K = int(input())
inf = 0
sup = 10**9
for i in range(100):
    mid = (inf+sup)/2.0
    if c(mid):
        inf = mid
    else:
        sup = mid
print(mid)