#include <bits/stdc++.h>
using namespace std;

int main() {
    int M, S[1500];
    cin >> M;
    for (int i = 0; i < 1 << M; i++) {
        cin >> S[i];
        S[i] *= S[i];
    }

    double dp[11][1500] = {};
    for (int i = 0; i < (1 << M); i++) {
        dp[0][i] = 1;
    }
    for (int i = 1; i <= M; i++) {
        for (int j = 0; j < (1 << M); j++) {
            int begin = (j ^ (1 << (i - 1))) & ~((1 << (i - 1)) - 1);
            for (int k = begin; k < begin + (1 << (i - 1)); k++) {
                dp[i][j] += dp[i - 1][j] * dp[i - 1][k] * S[j] / (S[j] + S[k]);
            }
        }
    }
    cout << fixed << setprecision(7) << dp[M][0] << endl;
}