/*
 * Title: P3317 [SDOI2014]重建
 * Source: 洛谷
 * URL: https://www.luogu.com.cn/problem/P3317
 * Author: Steven_lzx
 * Command: -std=c++17 -Wall -fno-ms-extensions
 * Date: 2022.11.5
 */
#include <bits/stdc++.h>
using namespace std;
const double EPS=1e-10;
int n;
double l[55][55];
int main()
{
    double ans=1,x,temp;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=n;j++)
        {
            scanf("%lf",&x);
            x+=EPS;
            if(i!=j)
            {
                l[i][j]=-x/(1-x);
                l[i][i]+=x/(1-x);
                if(i<j)
                    ans*=(1-x);
            }
        }
    }
    for(int i=2;i<=n;i++)
    {
        for(int j=i+1;j<=n;j++)
        {
            temp=l[j][i]/l[i][i];
            for(int k=i;k<=n;k++)
            {
                l[j][k]-=l[i][k]*temp;
            }
        }
        ans*=l[i][i];
    }
    printf("%.4lf\n",ans);
    return 0;
}