#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define MAXN 2325750
#define M 2510
using namespace std;
int n,tot,fa[M],num,ans;
struct nond{
    int x,y,z;
}edge[MAXN];
int cmp(nond a,nond b){
    return a.z<b.z;
}
int find(int x){
    if(fa[x]==x)    return fa[x];
    else return fa[x]=find(fa[x]);
}
int main(){
    freopen("mcst.in","r",stdin);
    freopen("mcst.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++){
            int x;
            scanf("%d",&x);
            if(x!=-1){
                edge[++tot].x=i;
                edge[tot].y=j;
                edge[tot].z=x;
            }
        }
    sort(edge+1,edge+1+tot,cmp);
    for(int i=1;i<=n;i++)    fa[i]=i;
    for(int i=1;i<=tot;i++){
        int dx=find(edge[i].x);
        int dy=find(edge[i].y);
        if(dx==dy)    continue;
        fa[dx]=dy;
        num++;
        ans+=edge[i].z;
        if(num==n-1)    break;
    }
    printf("%d",ans);
}