#include <bits/stdc++.h>
using namespace std;
typedef long 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;
		// cout << 1 << '\n';
		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];
			}
			// cout << A << ' ' << B << ' ';
			if (fabs(A) < 1e-10) {
				if (B > -1e-10) {
					b[pl[i]] = 0;
				} else {
					assert(0);
					memset(b, 0, sizeof(b));
					b[pl[i]] = 1;
				}
				W = 0;
				for (int j = 1; j <= n; j++) {
					for (int k = j + 1; k <= n; k++) {
						W += b[j] * b[k] * a[j][k];
					}
				}
				mxans = max(mxans, W);
				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;
			// cout << b[pl[i]] << '\n';
			db tW = A * best * best + B * best;
			W = 0;
			for (int j = 1; j <= n; j++) {
				for (int k = j + 1; k <= n; k++) {
					W += b[j] * b[k] * a[j][k];
				}
			}
			mxans = max(mxans, W);
			assert(fabs(W - tW) / max(fabs(W), (db)1) < 1e-10);
		}
		// puts("");
	} while (next_permutation(pl + 1, pl + n + 1));
	printf("%.10Lf\n", mxans);
}