#include<bits/stdc++.h> 
using namespace std;
int m,visi[550][550],safe[550][550],ways[4][2]={{1,0},{-1,0},{0,1},{0,-1}},x,y,t,ans=0x7fffffff;
struct node{
	int xx,yy,steps;
};
queue<node>q;
int bfs()
{
	node now,nex;
	now.xx=0,now.yy=0,now.steps=0; 
	visi[0][0]=0;
	q.push(now);
	while(!q.empty()){
		now=q.front();
		q.pop();
		if(safe[now.xx][now.yy]==0x7f7f7f7f)
			return ans=now.steps;
		for(int i=0;i<4;i++){
			if(now.xx+ways[i][0]>=0&&now.xx+ways[i][0]<=500&&now.yy+ways[i][1]>=0&&now.yy+ways[i][1]<=500){
				nex.xx=now.xx+ways[i][0],nex.yy=now.yy+ways[i][1],nex.steps=now.steps+1;
				if(safe[nex.xx][nex.yy]>nex.steps&&visi[nex.xx][nex.yy]){
					q.push(nex);
					visi[nex.xx][nex.yy]=0;
				}
			}
		}
	}
}
signed main()
{
	scanf("%d",&m);
	for(int i=0;i<=500;i++)
		for(int j=0;j<=500;j++)
			visi[i][j]=1;
	memset(safe,0x7f,sizeof(safe));
	for(int j=1;j<=m;j++)
	{
		scanf("%d%d%d",&x,&y,&t);
		safe[x][y]=min(safe[x][y],t);
		for(int i=0;i<4;i++)
			if(x+ways[i][0]>=0&&x+ways[i][0]<=500&&y+ways[i][1]>=0&&y+ways[i][1]<=500)
				safe[x+ways[i][0]][y+ways[i][1]]=min(safe[x+ways[i][0]][y+ways[i][1]],t);
	}
	bfs();
	if(ans==0x7fffffff)
		cout<<-1;
	else
		cout<<ans;
	return 0;
} 

第二个点莫名其妙的 $RE$ 了

输出是对，在线求调