#include <bits/stdc++.h>
using namespace std;
int n,m;
int tim[10010];//时间 
int x[10010],y[10010];//坐标 
int dp[10010];
int main (){
	cin >> n >> m;
	for (int i = 1 ; i <= m ; i ++){
		cin >> tim[i] >> x[i] >> y[i];
	}
	dp[1] = 1;
	for(int i = 2 ; i <= n ; i ++){
		if(abs(x[i]-x[i-1])+abs(y[i]-y[i-1])<=tim[i]-tim[i-1]){//判断是否能到达 
			dp[i] = dp[i-1]+1;
		}else{//不能就向前推； 
			dp[i] = dp[i-1];
			x[i] = x[i-1];
			y[i] = y[i-1];
			tim[i] = tim[i-1];
		}
	} 
	cout << dp[m];
	return 0;
}