M=int(input())
S=[int(input())**2 for i in range(2**M)]
N=2**M
p=[1]*N
for m in range(0,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[j]/(S[i]+S[j])
    q[i]*=p[i]*S[i]
  p=q
print(p[0]*S[0]*sum(p[j]/(S[0]+S[j]) for j in range(N//2, N)))