#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
using ll = long long;
int m;
vector<long double> s;
double dp[11][1<<10];
using P = pair<long double,int>;

void solve(){
	vector<P> vpii(1<<m);
	for(int i = 0;i < (1<<m);i++){
		vpii[i] = P(s[i],i);
	}
	for(int i =0;i<(1<<m);i++)dp[0][i] = 1;
	for(int i = 0;i<m;i++){
		for(int j = 0;j<(1<<m);j++){
			for(int k = 0;k<(1<<k);k++){
				if(vpii[j].second%2){
					if(vpii[j].second-1==vpii[k].second){
						dp[i+1][j] += dp[i][j]*dp[i][k]*((s[j]*s[j])/(s[j]*s[j]+s[k]*s[k]));
					}
				}else{
					if(vpii[j].second+1==vpii[k].second){
						dp[i+1][j] += dp[i][j]*dp[i][k]*((s[j]*s[j])/(s[j]*s[j]+s[k]*s[k]));
					}
				}
			}
		}
		for(int j = 0;j<(1<<m);j++){
			vpii[j].second/=2;
		}
	}
	printf("%.10lf\n",dp[m][0]);
}

signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cin >> m;
	s = vector<long double>(1<<m);
	for(auto &i:s)cin >> i;
	solve();
}