M=int(input())
s=[int(input())**2 for i in range(2**M)]
n=2**M
p=[1]*n 
for m in range(M-1):
    q=[0]*n 
    for i in range(n):
        b=((i>>m)^1)<<m 
        for j in range(b,b+(1<<m)):
            q[i]+=p[i]*s[i]*p[j]/(s[i]+s[j])
    p=q 
print(p[0]*s[0]*sum(p[j]/(s[0]+s[j]) for j in range(n//2,n)))