//It is coded by Ning_Mew on 5.6
#include<bits/stdc++.h>
using namespace std;

const int maxm=1e4+7;

int n,m;
int x[maxm],y[maxm],t[maxm];
int dp[maxm],ans=0;

int main(){
  scanf("%d%d",&n,&m);
  for(int i=1;i<=m;i++){
    scanf("%d%d%d",&t[i],&x[i],&y[i]);
    dp[i]=1;
    for(int j=1;j<i;j++){
      if(t[j]==t[i])break;
      if(abs(x[i]-x[j])+abs(y[i]-y[j])<=t[i]-t[j]) dp[i]=max(dp[i],dp[j]+1);
    }
    ans=max(ans,dp[i]);
  }
  printf("%d\n",ans);
  return 0;
}

//It is coded by Ning_Mew on 5.6
#include<bits/stdc++.h>
#define RE register
using namespace std;

const int maxm=1e4+7;

int n,m;
int x[maxm],y[maxm],t[maxm];
int dp[maxm],ans=0;

int main(){
  scanf("%d%d",&n,&m);
  for(RE int i=1;i<=m;i++){
    scanf("%d%d%d",&t[i],&x[i],&y[i]);
    dp[i]=1;
    for(RE int j=1;j<i;j++){
      //if(t[j]==t[i])break;
      if(abs(x[i]-x[j])+abs(y[i]-y[j])<=t[i]-t[j])
    dp[i]=max(dp[i],dp[j]+1);
    }
    ans=max(ans,dp[i]);
  }
  printf("%d\n",ans);
  return 0;
}