#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const long long N = 18;
const int base = 400;
long long n, m, t, ans, k, b[N], c[N], tong, cnt, q, d[N], h[N], lab[N], l[N],
    r[N];
mt19937_64 mt(chrono::steady_clock::now().time_since_epoch().count());
set<long long> st[N], st1[N];
struct point {
  long long x, y;
};
long double p[(1 << N)][N], a[N][N];
vector<pair<long long, pair<long long, long long> > > gr;
vector<long long> kq;
vector<pair<long long, long long> > adj[N];
string s;
long long pw(long long k, long long n) {
  long long total = 1;
  for (; n; n >>= 1ll) {
    if (n & 1) total = 1ll * total * k % mod;
    k = 1ll * k * k % mod;
  }
  return total;
}
long long A(long long u, long long v) {
  if (u > v) return 0;
  return b[v] * c[v - u] % mod;
}
long long findp(long long u) { return lab[u] < 0 ? u : lab[u] = findp(lab[u]); }
void hop(long long u, long long v) {
  if (lab[u] > lab[v]) swap(u, v);
  lab[u] += lab[v];
  lab[v] = u;
}
void add(long long id) {
  for (; id <= n; id += id & -id) ++d[id];
}
long long get(long long id) {
  long long total = 0;
  for (; id; id -= id & -id) total += d[id];
  return total;
}
long long lwr(long long x) {
  return lower_bound(kq.begin(), kq.end(), x) - kq.begin() + 1;
}
long long sa(long long n, long long m) {
  long long total = 0;
  for (int i = m; i <= n; i++) {
    total = (total + b[i] * pw(b[i - m], mod - 2) % mod) % mod;
  }
  return total;
}
long long C(long long u, long long v) {
  if (u > v) return 0;
  return b[v] * pw(b[u], mod - 2) % mod * pw(b[v - u], mod - 2) % mod;
}
bool cmp(const long long& x, const long long& y) { return c[x] < c[y]; }
long double cal(int bit, int x) {
  if (bit == (1 << n) - 1) return 1.0;
  if (p[bit][x] >= 0) return p[bit][x];
  long double mx = 0.0;
  if (!x) {
    for (int i = 0; i < n; i++) {
      if (!((bit >> i) & 1)) mx = max(mx, a[0][i] * cal(bit | (1 << i), 0));
    }
  } else {
    for (int i = 0; i < n; i++) {
      if ((bit >> i) & 1) continue;
      if (i) {
        mx = max(mx, a[i][x] * cal(bit | (1 << i), i) +
                         a[x][i] * cal(bit | (1 << i), x));
      } else {
        mx = max(mx, a[i][x] * cal(bit | (1 << i), i));
      }
    }
  }
  return p[bit][x] = mx;
}
void sol() {
  cin >> n;
  m = n * (n - 1) / 2;
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) {
      cin >> a[i][j];
    }
  if (n == 1) {
    cout << 1;
    return;
  }
  memset(p, -1.0, sizeof(p));
  long double res = 0;
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      if (i)
        res = max(res, a[i][j] * cal((1 << i) | (1 << j), i) +
                           a[j][i] * cal((1 << i) | (1 << j), j));
      else
        res = max(res, a[i][j] * cal((1 << i) | (1 << j), i));
    }
  }
  cout << fixed << setprecision(7) << res;
}
int main() {
  if (fopen("slingshot"
            ".in",
            "r")) {
    freopen(
        "slingshot"
        ".in",
        "r", stdin);
    freopen(
        "slingshot"
        ".out",
        "w", stdout);
  }
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int ntest = 1;
  while (ntest-- > 0) sol();
}
