孩子快疯了

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
import java.util.Arrays;

public class Main {
	
	static int n, m, ans;
	static int[][] rat = new int[10005][3];
	static int[] dp = new int[10005];
	
	static {
		Arrays.fill(dp, 1);
	}

	public static void main(String[] args) throws IOException {
		StreamTokenizer in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
		PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
		in.nextToken();
		n = (int) in.nval;
		in.nextToken();
		m = (int) in.nval;
		for (int i = 1, u, x1, y1; i <= m; i++) {
			in.nextToken();
			u = rat[i][0] = (int) in.nval;
			in.nextToken();
			x1 = rat[i][1] = (int) in.nval;
			in.nextToken();
			y1 = rat[i][2] = (int) in.nval;
			for (int j = 1, v, x2, y2; j < i; j++) {
				v = rat[j][0];
				x2 = rat[j][1];
				y2 = rat[j][2];
				if (Math.abs(x1-x2)+Math.abs(y1-y2) > u-v) continue;
				dp[u] = Math.max(dp[u], dp[v]+1);
			}
		}
		for (int i = 1; i <= m; i++) {
			ans = Math.max(ans, dp[i]);
		}
		out.println(ans);
		out.close();
	}

}