n = int(input())
a = list(map(int,input().split()))

count = [0]*(1<<n)
for i in range(1<<n):
    for j in range(n):
        if i>>j & 1:
            count[i] += a[j]

d = {}

def cal(s,t):
    if t <= 0:
        return 1
    if s == 0:
        return 0
    sta = s+ (t<<n)
    h = count[s]
    if sta in d:
        return d[sta]
    now = 0
    for i in range(n):
        if not s>>i & 1:
            continue
        nf = s^(1<<i)
        sco = 1
        for j in range(n):
            if not s>>j & 1:
                continue
            ns = s^(1<<j)
            p,q = 1/a[i],1/a[j]
            x,y = 1-cal(nf,h+1-t),cal(ns,t)
            v = (p*x+(1-p)*q*y)/(p+q-p*q)
            sco = min(sco,v)
        now = max(sco,now)
    d[sta] = now
    return now
print(cal((1<<n)-1,sum(a)//2+1))