#include<iostream>

#include<cstdio>

#include<cmath>

#include<cstdlib>

#include<cstring>

#include<algorithm>

using namespace std;

int read()

{

    int x=,f=;char c=getchar();

    while (c<''||c>'') {if (c=='-') f=-;c=getchar();}

    while (c>=''&&c<='') x=(x<<)+(x<<)+(c^),c=getchar();

    return x*f;

}

#define N 2010

int n,fa[N];

long long ans=;

struct data

{

    int x,y,z;

    bool operator <(const data&a) const

    {

        return z<a.z;

    }

}edge[N*N];

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

int main()

{

#ifndef ONLINE_JUDGE

    freopen("bzoj3714.in","r",stdin);

    freopen("bzoj3714.out","w",stdout);

    const char LL[]="%I64d\n";

#else

    const char LL[]="%lld\n";

#endif

    n=read();int t=;

    for (int i=;i<=n;i++)

        for (int j=i;j<=n;j++)

        t++,edge[t].x=i-,edge[t].y=j,edge[t].z=read();

    sort(edge+,edge+t+);

    for (int i=;i<=n;i++) fa[i]=i;

    for (int i=;i<=t;i++)

    if (find(edge[i].x)!=find(edge[i].y)) ans+=edge[i].z,fa[find(edge[i].x)]=find(edge[i].y);

    cout<<ans;

    return ;

}