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#include <cstdio>
#include <algorithm>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <cmath>
#include <map>
#include <string>
#include <set>
#include <cstring>
#include <iostream>
#include <sstream>
#include <cassert>
using namespace std;

#define PB push_back
#define FORE(i,t) for(typeof(t.begin())i=t.begin();i!=t.end();++i)
#define SZ(x) int((x).size())
#define REP(i,n) for(int i=0,_=(n);i<_;++i)
#define FOR(i,a,b) for(int i=(a),_=(b);i<=_;++i)
#define FORD(i,a,b) for(int i=(a),_=(b);i>=_;--i)

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

struct Edge {
  int cost, x, y;
  
  bool operator < (const Edge &e) const {
    return cost < e.cost;
  }
};

const int INF = 1e9 + 9;
const int MAX_N = 2002;

int fu_parent[MAX_N];

void fu_makeset(int x) {
  fu_parent[x] = -1;
}

int fu_find(int x) {
  if (fu_parent[x] < 0)
    return x;
  return fu_parent[x] = fu_find(fu_parent[x]);
}

void fu_union(int x, int y) {
  x = fu_find(x), y = fu_find(y);
  if (fu_parent[x] < fu_parent[y])
    fu_parent[y] = x;
  else if (fu_parent[x] > fu_parent[y])
    fu_parent[x] = y;
  else if (x != y) {
    fu_parent[y] = x;
    --fu_parent[x];
  }
}

void inline jeden() {
  int n;
  scanf("%d", &n);
  vector<Edge> edges;
  REP(i, n) {

    FOR(j, i + 1, n) {
      int cost;
      scanf("%d", &cost);
      edges.PB((Edge){cost, i, j});
    }
  }
  REP (i, n + 1) {
    fu_makeset(i);
  }
  sort(edges.begin(), edges.end());
  ll result = 0;
  FORE (edge, edges) {
    if (fu_find(edge->x) != fu_find(edge->y)) {
      fu_union(edge->x, edge->y);
      result += edge->cost;
    }
  }
  printf("%lld\n", result);
}

int main() {
  //int z; scanf("%d", &z); while(z--)
  jeden();
}