#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
const int N=1505,M=N*N;
struct edge{int u,v,w;}e[M];
int n,m,ans,f[N];
bool cmp(edge a,edge b){
    return a.w<b.w;
}
int found(int x){
    return f[x]==x?x:f[x]=found(f[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 w;
            scanf("%d",&w);
            if(w!=-1)e[++m]=edge{i,j,w};
            else e[++m]=edge{i,j,0x3f3f3f3f};
        }
    }
    sort(e+1,e+1+m,cmp);
    for(int i=1;i<=n;i++)f[i]=i;
    for(int i=1;i<=m;i++){
        int u=found(e[i].u);
        int v=found(e[i].v);
        if(u==v)continue;
        f[u]=v,ans+=e[i].w;
    }
    printf("%d\n",ans);
    return 0;
}