备注：
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#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <algorithm>
#include <map>
using namespace std;
#define int long long
const int N = 1e6 + 10;
const int INF = 0x3f3f3f3f;
struct node{
	int x, y, v;
}b[1000100];
int ans, n, pre[1000100], root1, root2, t;
struct gjl{
	int x, y, z, v;
}jb[2000100];
bool cmp(node aa, node bb)
{
	return aa.v < bb.v;
}
bool cmpx(gjl xx, gjl yy)
{
	return xx.x < yy.x;
}
bool cmpy(gjl xx, gjl yy)
{
	return xx.y < yy.y;
}
bool cmpz(gjl xx, gjl yy)
{
	return xx.z < yy.z;
}
int unionsearch(int root)
{
	int son, tmp;
	son = root;
	while(root != pre[root])
		root = pre[root];
	while(son != root)
	{
		tmp = pre[son];
		pre[son] = root;
		son = tmp;
	}
	return root;
}
signed main()
{
	//freopen(".in", "r", stdin);
	//freopen(".out", "w", stdout);
	cin>>n;
	for(int i = 1; i <= n; i++)
	{
		cin>>jb[i].x>>jb[i].y>>jb[i].z;
		jb[i].v = i;
	}
	sort(jb+1, jb+1+n, cmpx);
	for(int i = 2; i <= n; i++)
	{
		int k = jb[i].x - jb[i-1].x;
		int u = jb[i-1].v;
		int v = jb[i].v;
		b[++t].x = v;
		b[t].y = u;
		b[t].v = k;
	}
	sort(jb+1, jb+1+n, cmpy);
	for(int i = 2; i <= n; i++)
	{
		int k = jb[i].y - jb[i-1].y;
		int u = jb[i-1].v;
		int v = jb[i].v;
		b[++t].x = v;
		b[t].y = u;
		b[t].v = k;
	}
	sort(jb+1, jb+1+n, cmpz);
	for(int i = 2; i <= n; i++)
	{
		int k = jb[i].z - jb[i-1].z;
		int u = jb[i-1].v;
		int v = jb[i].v;
		b[++t].x = v;
		b[t].y = u;
		b[t].v = k;
	}
	sort(b+1, b+1+t, cmp);
	for(int i = 1; i <= n; i++)
	{
		pre[i] = i;
	}
	for(int i = 1; i <= t; i++)
	{
		int root1 = unionsearch(b[i].x);
		int root2 = unionsearch(b[i].y);
		if(root1 != root2)
		{
			ans += b[i].v;
			pre[root2] = root1;
		}
	}
	cout<<ans;
	return 0;
}