#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>

using namespace std;
const int N=3000100;

int fa[N>>2],w,js,answer,tot,n;
struct node{
	int x,y,dis;
}E[N];

inline int read()
{
	int x=0;int f=1;char c=getchar();
	while(c<‘0‘||c>‘9‘){if(c==‘-‘)f=-1;c=getchar();}
	while(c>=‘0‘&&c<=‘9‘)x=x*10+c-‘0‘,c=getchar();
	return x*f;
}

inline bool cmp(node a,node b)
{
	return a.dis<b.dis;
}

int getfa(int x)
{
	return fa[x]==x?x:fa[x]=getfa(fa[x]);
}

int main()
{
	freopen("mcst.in","r",stdin);
	freopen("mcst.out","w",stdout);
	n=read();
	for(int i=1;i<=n;i++)
		fa[i]=i;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
		{
			w=read();
			if(w!=-1&&j>i)
				E[++js].x=i,
				E[js].y=j,
				E[js].dis=w;
		}
	sort(E+1,E+js+1,cmp);
	for(int i=1;i<=js;i++)
	{
		int fx=getfa(E[i].x);
		int fy=getfa(E[i].y);
		if(fx!=fy)
		{
			tot++;
			fa[fx]=fy;
			answer+=E[i].dis;
			if(tot==n-1)
				break;
		}
	}
	printf("%d",answer);
	return 0;
}