M=int(input())
S=[int(input()) for i in range(1<<M)]

DP=[]
for i in range(1<<M):
    DP.append({i:1})

for tests in range(M):
    #print(DP)
    NDP=[]
    for i in range(0,len(DP),2):
        a=DP[i]
        b=DP[i+1]

        D=dict()

        for x in a:
            for y in b:
                k=S[x]
                l=S[y]

                Pk=k*k/(k*k+l*l)
                Pl=l*l/(k*k+l*l)

                if x in D:
                    D[x]+=a[x]*b[y]*Pk
                else:
                    D[x]=a[x]*b[y]*Pk

                if y in D:
                    D[y]+=a[x]*b[y]*Pl
                else:
                    D[y]=a[x]*b[y]*Pl
        NDP.append(D)

    #print(NDP)

    DP=NDP
                    
print(DP[0][0])