#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int maxn=1500*1500+5;

int u[maxn],v[maxn],w[maxn],cur,f[1505],r[maxn],o=0;
int n,x;
bool cmp(const int i,const int j){return w[i]<w[j];}
int find(int x){return f[x]==x?x:f[x]=find(f[x]);}

int kruscal(){
	int ans=0;
	for(int i=1;i<=n;i++) f[i]=i;
	for(int i=1;i<=cur;i++) r[i]=i;
	sort(r+1,r+cur+1,cmp);
	for(int i=1;i<=cur;i++){
		int e=r[i];
		int x=find(u[e]);
		int y=find(v[e]);
		if(x!=y){
			ans+=w[e];
			f[x]=y;
			o++; 
		}	
		if(o==n-1)
		    return ans;
	} 
	return ans;
}

int main(){
	freopen("wire.in","r",stdin);
	freopen("wire.out","w",stdout);
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	    for(int j=1;j<=n;j++){
	    	scanf("%d",&x);
	    	if(i<j&&x>0){
	    		cur++;
	    		u[cur]=i,v[cur]=j,w[cur]=x;
			}
		}
	int m=kruscal();
	printf("%d",m);
	return 0;
}