M=int(input())
S=[int(input())**2 for m in range(1<<M)]
def solve(S):
    N=len(S)
    if N==1:
        return [1]
    S0,S1=S[:N//2],S[N//2:]
    P0,P1=solve(S0),solve(S1)
    retu=[0]*N
    for i in range(N//2):
        for j in range(N//2):
            retu[i]+=P0[i]*P1[j]*S0[i]/(S0[i]+S1[j])
            retu[j+N//2]+=P0[i]*P1[j]*S1[j]/(S0[i]+S1[j])
    return retu
ans=solve(S)[0]
print(ans)