import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int m = sc.nextInt();
        int length = (1 << m);
        double[] strengths = new double[length];
        for (int i = 0; i < length; i++) {
            strengths[i] = sc.nextInt();
        }
        double[][] dp = new double[m + 1][length];
        Arrays.fill(dp[0], 1);
        for (int i = 1; i <= m; i++) {
            for (int j = 0; j < length; j++) {
                int start = j;
                start >>= i - 1;
                if (start % 2 == 0) {
                    start++;
                } else {
                    start--;
                }
                start <<= i - 1;
                for (int k = start; k < start + (1 << (i - 1)); k++) {
                    dp[i][j] += dp[i - 1][k] * Math.pow(strengths[j], 2) / (Math.pow(strengths[j], 2) + Math.pow(strengths[k], 2));
                }
                dp[i][j] *= dp[i - 1][j];
            }
        }
        System.out.println(dp[m][0]);
    }
}