#include <iostream>
#include <queue>
using namespace std;

int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};

int m;

struct pos{
	int safe,t;
	pos():safe(true){
	}
};
struct Node{
	int x,y,value;
};

pos danger[301][301];
bool vis[301][301];

void BFS();

int main(){
	cin>>m;
	int x,y,t;
	for(int i=0;i<m;i++){
		cin>>x>>y>>t;
		
		danger[x][y].safe=
		danger[x+1][y].safe=false;
		if(x!=0)
			danger[x-1][y].safe=false;
		danger[x][y+1].safe=false;
		if(y!=0)
			danger[x][y-1].safe=false;
		
		danger[x][y].t=
		danger[x+1][y].t=t;
		if(x!=0)
			danger[x-1][y].t=t;
		danger[x][y+1].t=t;
		if(y!=0)
			danger[x][y-1].t=t;
	}
	BFS();
	
	return 0;
}

void BFS(){
	queue<Node> q;
	Node head,tmp;
	head.value=head.x=head.y=0;
	q.push(head);
	
	while(!q.empty()){
		head=q.front();
		q.pop();
		if(danger[head.x][head.y].safe){
			cout<<head.value;
			return ;
		}
		for(int i=0;i<4;i++){
			tmp.value=head.value+1;
			tmp.x=head.x+dx[i];
			tmp.y=head.x+dy[i];
			if(danger[tmp.x][tmp.y].safe){
				q.push(tmp);
				continue;
			}
			if(danger[tmp.x][tmp.y].t>tmp.value)
				q.push(tmp);
			
		}
	}
}

样例无输出？