def Bisect_Int(ok,ng,is_ok):
    while abs(ok-ng)>1:
        mid=(ok+ng)//2
        if is_ok(mid):
            ok=mid
        else:
            ng=mid
    return ok

def Bisect_Float(ok,ng,is_ok,eps=1e-12,cnt=0):
    if cnt:
        for _ in range(cnt):
            mid=(ok+ng)/2
            if is_ok(mid):
                ok=mid
            else:
                ng=mid
    else:
        while abs(ok-ng)>eps:
            mid=(ok+ng)/2
            if is_ok(mid):
                ok=mid
            else:
                ng=mid
    return ok

N=int(input())
L=list(map(int,input().split()))
K=int(input())
def is_ok(x):
    cnt=0
    for l in L:
        cnt+=l//x
    return cnt>=K
ans=Bisect_Float(1e-7,1e10,is_ok,eps=1e-9)
print(ans)