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)