#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000

int main(){
	
	int M;
	cin>>M;
	
	vector<double> dp(1<<M,1.0);
	
	vector<double> s(1<<M);
	rep(i,1<<M)cin>>s[i];
	
	rep(i,M){
		vector<double> ndp(1<<M);
		
		rep(j,1<<M){
			rep(k,1<<M){
				if(j==k)continue;
				if((j>>(i+1))==(k>>(i+1)) && (j>>(i))!=(k>>(i))){
					
					ndp[j] += dp[j] * dp[k] * pow(s[j],2.0) / (pow(s[j],2.0) + pow(s[k],2.0));
					
				}
			}
		}
		swap(dp,ndp);
		
	}
	
	cout<<fixed<<setprecision(10)<<dp[0]<<endl;
	
	return 0;
}