#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

double p(int x, int y) {
	return (double)(x * x) / (x * x + y * y);
}

int main() {
	int M; cin >> M;
	int m = 1 << M;
	vector<int> S(m);
	for (int i = 0; i < m; i++) cin >> S[i];
	vector<double> dp(m, 1);
	int mask = 1;
	for (int k = 0; k < M; k++) {
		vector<double> _dp(m, 0);
		for (int i = 0; i < m; i++)
			for (int j = 0; j < m; j++)
				if ((i ^ j) >> k == 1)
					_dp[i] += dp[i] * dp[j] * p(S[i], S[j]);
		dp = _dp;
	}
	printf("%.10f\n", dp[0]);
}