m,*a = map(int,open(0).read().split())
M = 1<<m
for i in range(M): a[i] **= 2
dp = [1.0]*M
for i in range(m):
    ndp = dp[:]
    L = 1<<i
    for j in range(1<<(m-i-1)):
        for k in range(1<<i):
            nk = j*2+k
            v = w = 0
            for r in range(1<<i):
                v += dp[j*L*2+L+r]*(a[nk]/(a[nk]+a[j*L*2+L+r]))
                w += dp[j*L*2+r]*(a[nk+L]/(a[nk+L]+a[j*L*2+r]))                
            ndp[nk] *= v
            ndp[nk+L] *= w
    dp = ndp
print(dp[0])