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#include <algorithm>
#include <cstdio>
#include <vector>

using namespace std;

typedef vector<pair<int, pair<int, int> > > Vector;

vector<int> parent;

void Init(const int n) {
  parent.resize(0);
  parent.resize(n, -1);
}

int Find(int a) {
  int b = a;
  while (parent[b] >= 0) b = parent[b];
  while (a != b) {
    const int c = parent[a];
    parent[a] = b;
    a = c;
  }
  return a;
}

void Union(const int a, const int b) {
  if (parent[a] < parent[b]) {
    parent[a] += parent[b];
    parent[b] = a;
  } else {
    parent[b] += parent[a];
    parent[a] = b;
  }
}

int main() {
  int n;
  scanf("%d", &n);
  Vector v;
  for (int i = 0; i < n; ++i) for (int j = i + 1; j <= n; ++j) {
    int c;
    scanf("%d", &c);
    v.push_back(make_pair(c, make_pair(i, j)));
  }
  sort(v.begin(), v.end());
  long long ret = 0;
  Init(n + 1);
  for (int k = 0; k < v.size(); ++k) {
    const int i = Find(v[k].second.first);
    const int j = Find(v[k].second.second);
    if (i != j) {
      Union(i, j);
      ret += v[k].first;
    }
  }
  printf("%lld\n", ret);
  return 0;
}