#include <bits/stdc++.h>
#define f first
#define s second
#define mp make_pair
#define pb push_back
#define loop(i,a,n) for(int i=a;i<=n;i++)
#define mod 1000000007
#define eps 1e-9
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef set<int> si;
typedef map<int, int> mii;

int n,x;
float dp[19][265000],probs[19][19],ans;
bool vis[19][265000];

float solve(int fr, int mask){
    if(mask == ((1<<(n))-2)) return  probs[1][fr];
    if(vis[fr][mask]) return dp[fr][mask];

    vis[fr][mask] = true;
    float first = 0, second = 0;
    float ans = 0 ;
        loop(i,1,n-1){
            if(!(mask&(1<<i))){
                first = probs[fr][i+1]*solve(fr, mask|(1<<i));
                second = probs[i+1][fr]*solve(i+1, mask|(1<<i));
                ans = max(ans , first + second) ;
            }
        }

    return dp[fr][mask] = ans;
}

int main(){
    cin >>n;
    loop(i,1,n){
        loop(j,1,n){
            cin >>probs[i][j];
        }
    }
    if(n == 1){
        cout <<1;
        return 0;
    }
    loop(i,2,n){
        x = 0;
        x|=(1<<(i-1));
        ans = max(ans, solve(i, x));
    }

    printf("%.6f", ans);
}