#include <bits/stdc++.h>
using namespace std;

const int MAXN(15), MAXEPOCH(3e6);

int n;
double A[MAXN][MAXN], M[MAXN][MAXN];
double u[MAXN], v[MAXN];
double du[MAXN], dv[MAXN];

double myexp(double x) {
	if (x > 1e36) return 1e36;
	else if (x < -1e36) return 1e-36;
	return exp(x);
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			scanf("%lf", &A[i][j]);
		}
	}
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			M[i][j] = A[i][j];
		}
	}

	for (double rate = 1. / n; rate >= 0.01; rate /= 10) {
		for (int epoch = 0; epoch < MAXEPOCH; epoch++) {
			double sumv = 0; 
			for (int i = 1; i <= n; i++) sumv += myexp(v[i]);
			for (int i = 1; i <= n; i++) u[i] = myexp(v[i]) / sumv;
			
			for (int i = 1; i <= n; i++) {
				du[i] = 0;
				for (int j = 1; j <= n; j++) {
					du[i] += M[i][j] * u[j];
				}
			}
			for (int i = 1; i <= n; i++) {
				dv[i] = 0;
				for (int j = 1; j <= n; j++) {
					if (i == j) dv[i] += du[j] * u[j] * (1 - u[j]);
					else dv[i] -= du[j] * u[i] * u[j];
				}
			}
			for (int i = 1; i <= n; i++) v[i] += rate * dv[i];
		}
	}

	double sumv = 0; 
	for (int i = 1; i <= n; i++) sumv += exp(v[i]);
	for (int i = 1; i <= n; i++) u[i] = exp(v[i]) / sumv;

	double ans = 0;
	for (int i = 1; i <= n; i++) {
		for (int j = i + 1; j <= n; j++) {
			ans += u[i] * u[j] * A[i][j];
		}
	}
	printf("%.9lf\n", ans);

	return 0;
}