#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP(i,n,0)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 1e8

typedef long long ll;

double prob(double a, double b) {
    return a*a/(a*a+b*b);
}

int main() {
    int i, j, k, m;
    double ans = 1;
    double s[1<<10];
    double p[11][1<<10];
    cin >> m;
    rep (i,1<<m) cin >> s[i];
    fill (p[0],p[0]+(1<<m),1);
    REP (i,1,m+1) {
        rep (j,1<<m) {
            p[i][j] = 0;
            int base = j/(1<<i)*(1<<i);
            rep (k,1<<i) {
                if (j/(1<<(i-1)) != (base+k)/(1<<(i-1)))
                    p[i][j] += p[i-1][base+k]*prob(s[j],s[base+k]);
            }
            p[i][j] *= p[i-1][j];
        }
    }
    cout << p[m][0] << endl;
    return 0;
}