#include <bits/stdc++.h>
#include <stdio.h>
#include <stdlib.h>

/// Defines
#define all(a) a.begin(),a.end()
#define ios std::ios::sync_with_stdio(false);

/// STL
#define vi vector<int>
#define vvi vector< vector<int> >
#define pb push_back
#define mp make_pair
#define mii map<int,int>
#define pii pair<int,int>

/// Iterator
#define forit(it, s) for(__typeof(s.begin()) it = s.begin(); it != s.end(); it++)

/// Constants
#define ll long long
#define mod 1000000007
#define EPS 1e-7
#define INF 2000000007
#define LINF 9000000000000000007

/// File I/O
#define READ(f) freopen(f, "r", stdin)
#define WRITE(f) freopen(f, "w", stdout)

using namespace std;

int n;
float matrix[20][20], dp[20][1 << 18];
bool checked[20][1 << 18];

float solve(int index, int mask);

int main()
{
    cin >> n;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
            cin >> matrix[i][j];
    }
    memset(dp, -1, sizeof(dp));
    float ans = 0;
    for (int i = 0; i < n; i++)
    {
        ans = max(ans, solve(i, (1 << i)));
    }
    cout << fixed << setprecision(6) << ans << endl;

    /// That's all folks.
    return 0;
}

float solve(int index, int mask)
{
    if (mask == (1 << n) - 1)
    {
        if (index == 0)
            return 1;
        else
            return 0;
    }

    if (checked[index][mask])
        return dp[index][mask];

    float sum = 0;
    for (int i = 0; i < n; i++)
    {
        if ((mask & (1 << i)) == 0)
        {
            sum = matrix[index][i] * solve(index, mask | (1 << i));
            sum += matrix[i][index] * solve(i, mask | (1 << i));
        }
    }
    checked[index][mask] = true;
    return dp[index][mask] = sum;
}