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#include<cstdio>
#include<vector>
#include<set>
using namespace std;
 
const int inf = 1000000003;
int n,m;
vector< vector< pair<int,int> > > adj;
vector<bool> vis;
vector<int> waga;
 
struct cmp
{
	bool operator() (const int &a, const int &b)
	{
		if (waga[a] < waga[b]) return true;
		if (waga[a] > waga[b]) return false;
		return a<b;
	}
};
 
set<int, cmp> kopiec;
 
void prim_dijkstra(int s)
{
	int i,v,u,c;
	waga.clear(); waga.resize(n, inf); 
	vis.clear(); vis.resize(n,false);
 
	waga[s] = 0;
	kopiec.clear(); for (i=0; i<n; i++) kopiec.insert(i);

 
	while( !kopiec.empty() )
	{
		u = *(kopiec.begin()); 
		kopiec.erase(kopiec.begin());
		vis[u]=true; 
 
		for (i=0; i<adj[u].size(); i++)
		{
			v = adj[u][i].first;
			if (!vis[v])
			{
				c = adj[u][i].second;
				if (c < waga[v]) 
				{
					kopiec.erase(kopiec.find(v));
					waga[v] = c; 
					kopiec.insert(v);
				}
			}
		}
	}
}
 
int main(void)
{
	int c,i,j;
 
	scanf("%d", &n); m = (n*(n+1))/2;	
	n++;
	adj.resize(n);
	
	for (i=0; i<n; i++)
		for(j=i+1; j<n; j++)
	{
		scanf("%d",&c); 
		adj[i].push_back(make_pair(j,c));
		adj[j].push_back(make_pair(i,c));
	}
 
	prim_dijkstra(0); 
 
	long long int suma = 0; 
	for (i=1; i<n; i++) suma += waga[i]; 
 
	printf("%lld\n", suma);
	return 0;
}