import sys

sys.setrecursionlimit(200005)
def II(): return int(sys.stdin.buffer.readline())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))

popcnt = lambda x: bin(x).count("1")

n = II()
aa = LI()

tot = sum(aa)
P = {}
finish = (1 << n)-1

# 初期化
for s in range(1 << n):
    t = finish ^ s
    x = sum(a for i, a in enumerate(aa) if s >> i & 1)
    y = tot-x
    P[s, t] = (x > y)*1

# DP
for used in range(finish-1, -1, -1):
    # 2人の取ったカードを合わせたのがusedで、その部分集合をsとして回す
    s = used
    while 1:
        t = used ^ s
        val = 0
        for i, ai in enumerate(aa):
            if used >> i & 1: continue
            si = s | 1 << i

            # p1を求める
            p1 = 1
            if popcnt(used) == n-1:  # 先手が最後の1枚を取った場合
                p1 = P[si, t]
            else:
                for j, aj in enumerate(aa):
                    if j == i: continue
                    if used >> j & 1: continue
                    p1 = min(p1, P[si, t | 1 << j]/aj+P[si, t]*(aj-1)/aj)

            # kを全探索する
            mn = 1  # iを固定したときのPの最小値
            for k, ak in enumerate(aa):
                if used >> k & 1: continue
                tk = t | 1 << k
                mn = min(mn, (ak*p1+(ai-1)*P[s, tk])/(ai+ak-1))

            val = max(val, mn)

        P[s, t] = val

        if s == 0: break
        s = (s-1) & used

print(P[0, 0])