import sequtils,strutils

var
    M = stdin.readline.parseInt
    S = newSeq[float64](0)
    S2 = newSeqWith(M + 1, newSeq[float64](1 shl M))

for i in 0..<(1 shl M):
    S2[0][i] = 1
for m in 0..<(1 shl M):
    S.add(stdin.readline.parsefloat)

for m in 0..<M:
    for i,s in S:
        var j = ((1 shl M) + i) shr m
        j = (j xor 1)
        j = (j shl m)
        for k in 0..<(1 shl m):
            var p = j + k - (1 shl M)
            S2[m + 1][i] += s * s * S2[m][i] * S2[m][p] / (s * s + S[p] * S[p])
echo S2[M][0]