#include "bits/stdc++.h"
using namespace std;
#ifdef _DEBUG
#include "dump.hpp"
#else
#define dump(...)
#endif

//#define int long long
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(c) begin(c),end(c)
const int INF = sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = (int)(1e9) + 7;
const double PI = acos(-1);
const double EPS = 1e-9;
template<class T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, const T &b) { if (a > b) { a = b; return true; } return false; }

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N; cin >> N;
	vector<vector<int>>v(N, vector<int>(N));
	rep(i, 0, N)rep(j, 0, N)cin >> v[i][j];
	vector<pair<int, int>>m(N, pair<int, int>(-1, -1)), w(m);// 相手、スコア
	queue<int>q;
	rep(i, 0, N)q.push(i);
	while (!q.empty()) {
		int x = q.front(); q.pop();
		int index = distance(v[x].begin(), max_element(all(v[x])));
		if (w[index].second < v[x][index]) {
			w[index].second = v[x][index];
			if (w[index].first != -1) {
				v[w[index].first][index] = -1;
				q.push(w[index].first);
			}
			w[index].first = x;
		}
		else {
			v[x][index] = -1;
			q.push(x);
		}
	}
	int ans(0);
	rep(i, 0, N)ans += w[i].second;
	cout << ans / 2 << endl;
	return 0;
}