#include<bits/stdc++.h>
#define COGS
using namespace std;
const int maxn=1600;
struct edge{
	int from,to,cost;
	edge(int u,int v,int d):from(u),to(v),cost(d){}
	bool operator <(const edge&rhs)const{
		return cost<rhs.cost;
	}
};
vector<edge> E;
vector<int> G[maxn];
int n,temp,cnt,ans;
int f[maxn];
inline int ff(int x){
	if (f[x]==x) return x;
	else return f[x]=ff(f[x]);
}
inline bool merge(int x,int y){
	int a=ff(x),b=ff(y);
	if (a==b) return false;
	else{
		f[a]=b;
		return true;
	}
}
inline void init(int n){
	for (int i=1;i<=n;i++){
		f[i]=i;
	}
}
inline void in(){
	#ifdef COGS
	freopen("wire.in","r",stdin);
	freopen("wire.out","w",stdout);
	#endif
	scanf("%d",&n);init(n);
	for (int i=1;i<=n;i++){
		for (int j=1;j<=n;j++){
			scanf("%d",&temp);
			if (temp==0) continue;
			E.push_back(edge(i,j,temp));
			cnt++;
		}
	}
}
inline void deal(){
	//printf("%d\n",cnt);
	sort(E.begin(),E.end());
	for (int i=0;i<cnt;i++){
		edge &e=E[i];//printf("%d %d %d\n",e.from,e.to,e.cost);
		if (merge(e.from,e.to)){
			ans+=e.cost;
			//printf("USE\n");
		}
	}
}
inline void p(){
	printf("%d",ans);
}
int Main(){
	in();
	deal();
	p();
	return 0;
}
int main(){;}
int xlm=Main();