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#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <cmath>
#include <cstring>
#include <string>
#include <iostream>
#include <complex>
#include <sstream>
using namespace std;
 
typedef long long LL;
typedef unsigned long long ULL;
typedef long double LD;
typedef vector<int> VI;
typedef pair<int,int> PII;
 
#define REP(i,n) for(int i=0;i<(n);++i)
#define SIZE(c) ((int)((c).size()))
#define FOR(i,a,b) for (int i=(a); i<(b); ++i)
#define FOREACH(i,x) for (__typeof((x).begin()) i=(x).begin(); i!=(x).end(); ++i)
#define FORD(i,a,b) for (int i=(a)-1; i>=(b); --i)
#define ALL(v) (v).begin(), (v).end()
 
#define pb push_back
#define mp make_pair
#define st first
#define nd second

vector<pair<int, PII> > V;

vector<int> E[3000];
bool covered[2005][2005];

void cover(int l, int r) {
  if (l > r) {
    swap(l,r);
  }
  if (covered[l][r]) return;
  covered[l][r] = true;
  E[l].push_back(r);
  E[r].push_back(l);
}

void scase() {
  V.clear();
  int N;
  scanf("%d",&N);
  REP(i,N)FOR(j,i+1,N+1) {
    int X;
    scanf("%d",&X);
    V.push_back(mp(X, PII(i+1,j+1)));  
  }
  sort(V.begin(), V.end());
  REP(i,N+3) {
    REP(j,N+3) covered[i][j] = false;
    E[i].clear();
    E[i].push_back(i);
  }
  
  LL result = 0;
  FOREACH(it, V) {
    int a = it->nd.st;
    int b = it->nd.nd;
    if (covered[a][b]) continue;

    int J = E[a].size();
    int K = E[b].size();
    REP(j,J)REP(k,K) {
      int jt = E[a][j];
      int kt = E[b][k];
      cover(jt, kt);
    }
    result += it->st;
  }

  printf("%lld\n", result);
}

int main() {
  scase();
}