#include <bits/stdc++.h>
using namespace std;
typedef double db;
typedef pair<int, int> pr;
int n, pl[12];
db a[12][12], mxans = 0, b[12];
int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		pl[i] = i;
		for (int j = 1; j <= n; j++) cin >> a[i][j];
	}
	do {
		memset(b, 0, sizeof(b));
		b[pl[1]] = 1;
		db W = 0;
		for (int i = 2; i <= n; i++) {
			db A = W, B = 0;
			for (int k = 1; k <= n; k++) {
				A -= a[pl[i]][k] * b[k];
				B += a[pl[i]][k] * b[k];
			}
			if (fabs(A) < 1e-10) {
				b[pl[i]] = 0;
				continue;
			}
			db best = -B / A / 2;
			best = min((db)1, max(best, (db)0));
			for (int k = 1; k <= n; k++) b[k] *= best;
			b[pl[i]] = 1 - best;
			W = A * best * best + B * best;
		}
		if (W < mxans * 0.8) continue;
		for (int i = 1; i <= n; i++) {
			db Uu = 0;
			for (int k = 1; k <= n; k++) {
				Uu += b[k] * a[i][k];
			}
			for (int j = i + 1; j <= n; j++) {
				db sum = b[i] + b[j];
				db U = Uu - b[j] * a[i][j];
				db V = 0;
				for (int k = 1; k <= n; k++) {
					if (k != i) V += b[k] * a[j][k];
				}
				db A = -a[i][j];
				db B = a[i][j] * sum + U - V;
				if (!a[i][j]) {
					if (B > 0) b[i] = sum, b[j] = 0;
					else b[j] = sum, b[i] = 0;
					continue;
				}
				db best = -B / A / 2;
				best = min(sum, max(best, (db)0));
				b[i] = best, b[j] = sum - best;
				Uu = U + b[j] * a[i][j];
			}
		}
		// cout << W << '\n';
		W = 0;
		for (int i = 1; i <= n; i++) {
			for (int j = i + 1; j <= n; j++) {
				W += b[i] * b[j] * a[i][j];
			}
		}
		// cout << W << '\n';
		// cout << '\n';
		mxans = max(mxans, W);
	} while (next_permutation(pl + 1, pl + n + 1));
	printf("%.10lf\n", mxans);
}