#include<bits/stdc++.h>
using namespace std;
int ans=INT_MAX;
int n;
int a[310][310];
int dx[4]={0,1,0,-1};
int dy[4]={1,0,-1,0};
struct node{
	int x,y,step;
	node(int xx,int yy,int st){
		x=xx; y=yy; step=st;
	}
};
queue<node> q;
void bfs(){
	q.push(node(0,0,0));
	while(!q.empty()){
		node nd=q.front(); q.pop();
		if(a[nd.x][nd.y]>=0x7f){
			ans=min(ans,nd.step);
			continue;
		}
		for(int i=0;i<4;i++){
			int xx=nd.x+dx[i];
			int yy=nd.y+dy[i];
			if(xx>=0&&yy>=0&&a[xx][yy]>nd.step+1){
				q.push(node(xx,yy,nd.step+1));
			}
		}
	}
}
int main(){
	memset(a,0x7f,sizeof(a));
	cin>>n;
	for(int i=1;i<=n;i++){
		int x,y,w;
		cin>>x>>y>>w;
	    a[x][y]=min(w,a[x][y]);
		for(int i=0;i<4;i++){
			int xx=x+dx[i];
			int yy=x+dy[i];
			if(xx>=0&&yy>=0) a[xx][yy]=min(a[xx][yy],w);
		}
	}
	bfs();
	cout<<ans;
	return 0;
}