#include <bits/stdc++.h>
#define rep(i, n) for (lli i = 0; i < (n); i++)
#define rrep(i, n) for (lli i = (n)-1; i >= 0; i--)
using namespace std;
using lli = long long int;
double s[2005];
double p(int i, int j)
{
    return s[i] * s[i] / (s[i] * s[i] + s[j] * s[j]);
}
int main()
{
    int m;
    cin >> m;
    double dp[11][1 << 11] = {};
    rep(j, 1 << m)
    {
        cin >> s[j];
        dp[0][j] = 1.0;
    }

    rep(j, m)
    {
        rep(i, 1 << m)
        {
            double pos = 0;
            rep(l, 1 << j)
            {
                int idx = ((i ^ 1 << j) & ~((1 << j) - 1)) + l;
                pos += p(i, idx) * dp[j][idx];
            }
            pos *= dp[j][i];
            dp[j + 1][i] = pos;
        }
    }
    cout << dp[m][0] << endl;
}