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#include <iostream>
#include <vector>
#include <algorithm>
#include <cassert>
#include <queue>
#include <stack>

#define NDEBUG
using namespace std;
int n;
vector< pair< int, pair<int,int> > > pairs;
bool dirty_check[2001][2001];
int next2[2001];
int prev2[2001];
const int NONE = 0;

bool is_checked(int a, int b)
{
    int pos = a;
    while(pos<=n)
    {
        if(next2[pos]==NONE)
            return false;
        if(next2[pos]==b)
            return true;
        pos = next2[pos]+1;
    }
    return false;
}

void check(int a, int b)
{
    stack< pair<int,int>, vector<pair<int,int> > > s;
    s.push(make_pair(a,b));
    while(!s.empty())
    {
        a = s.top().first;
        b = s.top().second;
        s.pop();
        assert(a<=b);

        if(dirty_check[a][b])
            continue;
        dirty_check[a][b] = true;

        if(next2[a]!=NONE )
        {
            if(next2[a]==b)
            {
                continue;
            }
            else if(next2[a]<b)
            {
                s.push(make_pair(next2[a]+1,b));
            }
            else if(next2[a]>b)
            {
                int c = next2[a];
                prev2[c] = NONE;
                next2[a] = NONE;
                s.push(make_pair(b+1,c));
            }
        }
        if(prev2[b]!=NONE )
        {
            if(prev2[b]==a)
                continue;
            else if(prev2[b]>a)
            {
                s.push(make_pair(a,prev2[b]-1));
            }
            else if(prev2[b]<a)
            {
                int c = prev2[b];
                next2[c] = NONE;
                prev2[b] = NONE;
                s.push(make_pair(c,a-1));
            }
        }
        if(prev2[b]==NONE && next2[a]==NONE)
        {
            prev2[b] = a;
            next2[a] = b;
        }
    }
}
long long int solve()
{
    long long int total_cost = 0;

    sort(pairs.begin(),pairs.end());
    assert(pairs.size()==n*(n+1)/2);
    int inserted = 0;
    for(unsigned int i=0; i<pairs.size(); ++i)
    {
        int cost = pairs[i].first;
        int a = pairs[i].second.first;
        int b = pairs[i].second.second;
        if( is_checked(a,b) == false )
        {
            check(a,b);
            total_cost += cost;
            ++inserted;
            if(inserted>=n)
                break;
        }
    }
    return total_cost;
}

void read(int n)
{
    for(int i=1;i<=n;++i)
        for(int j=i;j<=n;++j)
        {
            int cost;
            cin >> cost;
            pairs.push_back(make_pair(cost,make_pair(i,j)));
        }
}
int main()
{
    cin.sync_with_stdio(0);
    cin >> n;
    read(n);
    cout << solve();
    return 0;
}