M=int(raw_input())
S=[int(raw_input()) for i in xrange(1<<M)]
prob=[[0.0 for i in xrange(1<<M)] for j in xrange(M+1)]
for i in xrange(1<<M):
    prob[0][i]=1.0
for j in xrange(1,M+1):
    n_group=1<<j
    for a in xrange((1<<M)/n_group):
        for left in range(a*n_group,a*n_group+n_group/2):
            if a==0 and left > 0:
                break
            for right in range(a*n_group+n_group/2,(a+1)*n_group):
                #print j,":",left,"-",right
                prob[j][left] += prob[j-1][left]*prob[j-1][right]*S[left]*S[left]/(S[left]*S[left]+S[right]*S[right])
                prob[j][right] += prob[j-1][left]*prob[j-1][right]*S[right]*S[right]/(S[left]*S[left]+S[right]*S[right])
    #for a in xrange(1<<M):
    #    print prob[j][a],
    #print
print prob[M][0]