#include <iostream>
#include<vector>
#include<queue>
using namespace std;
int mp[310][310]={0},st[310][310]={0};
int m;//流星数量
int dx[]={1,-1,0,0};
int dy[]={0,0,1,-1};
int ans = -1; // 记录答案
struct node{
	int x,y,t;
};
deque<node> q;
void bfs(){
	q.push_front({0,0,0});
	st[0][0] =1;
	while(!q.empty()){
		auto t = q.front();q.pop_front();
		int ti = t.t;
		for(int i=0;i<4;i++){
			int x = t.x+dx[i], y =t.y+dy[i];
			if(x>300 || x<0 || y >300 || y<0) continue;
			if(ti+1>=mp[x][y] && mp[x][y]!=-1) continue;
			if(st[x][y]!=0) continue;
			if(mp[x][y] ==-1){
				if(ans ==-1) ans = ti+1;
				else{
					ans = min(ans,ti+1);
				}
			}
			st[x][y] = 1;
			q.push_back({x,y,ti+1});
		}
	}
}
int main(){
	for(int i=0;i<310;i++){
		for(int j=0;j<310;j++) mp[i][j] = -1;
	}
	cin>>m;
	while(m--){
		int x,y,t;
		cin>>x>>y>>t;
		if(mp[x][y] ==-1) mp[x][y] = t;
		else{
			mp[x][y] = min(mp[x][y],t);
		}
		for(int i=0;i<4;i++){
			int xx = x+dx[i], yy = y+dy[i];
			if(xx>300 || xx<0 || yy >300 || yy<0) continue;
			if(mp[xx][yy] ==-1 ) mp[xx][yy] = t;
			else{
				mp[xx][yy] = min(mp[xx][yy],t);
			}
		}
	}
//	for(int i=0;i<=10;i++){
//		for(int j=0;j<=10;j++){
//			cout<<mp[i][j]<<" ";
//		}
//		cout<<endl;
//	}
	bfs();
	cout<<ans;
}