#include<bits/stdc++.h>
using namespace std;
int p[1001][1001],n,m,nt=1;
struct mouse
{
	int time;
	int x;
	int y;
}mouse[10001];
int sl(int rx,int ry,int ans)
{
	if(rx>n||rx<0||ry<0||ry>n)return 0;
	int i=0,x=0;
	while(mouse[nt+i].time==nt)
	{
		int dis=abs(rx-mouse[nt+i].x)+abs(ry-mouse[nt+i].y);
		if(dis==1||dis==0)
		{
			mouse[nt].time=0;
		}
	}
	nt++;
	if(x>ans)return x;
	else
		return max(max(sl(rx+1,ry,ans),sl(rx-1,ry,ans)),max(sl(rx,ry-1,ans),sl(rx,ry+1,ans)));
}
int main()
{
	//freopen("model.in","r",stdin);
	struct mouse;
	cin>>n>>m;
	for(int i=1;i<=m;i++)
	{
		cin>>mouse[i].time>>mouse[i].x>>mouse[i].y;
	}
	for(int i=1;i<=m-1;i++)
	{
		for(int j=1;j<=m;j++)
		{
			bool flag=0;
			if(mouse[j].time>mouse[j+1].time)
			{
				swap(mouse[j].time,mouse[j+1].time);
				swap(mouse[j].x,mouse[j+1].x);
				swap(mouse[j].y,mouse[j+1].y);
				flag=1;
			}
		}
		if(!flag)break;
	}
	cout<<sl();
	return 0;
}

34行输入为什么错呢？ ：（ 求教