#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
typedef pair<int, int> pr;
int n;
double w[15][15], a[15], sw[15];
int main() {
	cin >> n;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++) cin >> w[i][j];
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++) sw[i] += w[i][j];
	a[1] = 1;
	for (int kk = 1; kk <= 50000; kk++) {
		for (int i = 1; i <= n; i++) {
			for (int j = i + 1; j <= n; j++) {
				db sum = a[i] + a[j];
				db U = 0;
				db V = 0;
				for (int k = 1; k <= n; k++) {
					if (k != j) U += a[k] * w[i][k];
					if (k != i) V += a[k] * w[j][k];
				}
				db A = -w[i][j];
				db B = w[i][j] * sum + U - V;
				if (!w[i][j]) {
					if (B > 0) a[i] = sum, a[j] = 0;
					else a[j] = sum, a[i] = 0;
					continue;
				}
				db best = -B / A / 2;
				best = min(sum, max(best, (db)0));
				a[i] = best, a[j] = sum - best;
			}
		}
	}
	db ans = 0;
	for (int i = 1; i <= n; i++)
		for (int j = i + 1; j <= n; j++) ans += w[i][j] * a[i] * a[j];
	printf("%.10lf\n", ans);
}