N = int(input())
LENGTHS = list(map(int, input().split()))
K = int(input())

LENGTHS.sort()
l = 0
r = LENGTHS[-1]
for i in range(100):
    m = (l + r)/2
    counts = 0
    for length in LENGTHS:
        counts += length//m
    if K <= counts:
        l = m
    else:
        r = m
print("%.15f" % l)