#include <bits/stdc++.h>   using namespace std;   int main() {     int q = 1, i, j;     while (q--) {       int n, r;       cin >> r >> n;       vector<int> t(n + 1), x(n + 1), y(n + 1);       t[0] = 0, x[0] = 1, y[0] = 1;       for (i = 1; i < (n + 1); i++) {         cin >> t[i] >> x[i] >> y[i];       }       vector<int> dp(n + 1, INT_MIN), pref(n + 1, INT_MIN);       dp[0] = 0;       for (i = 1; i < (n + 1); i++) {         dp[i] = 1 + pref[max(i - 2 * r, 0)];         for (j = max(0, i - 2 * r + 1); j < (i); j++) {           if (t[i] - t[j] >= abs(x[i] - x[j]) + abs(y[i] - y[j])) {             dp[i] = max(dp[i], dp[j] + 1);           }         }         pref[i] = max({dp[i], pref[i - 1], 0});       }       cout << pref[n] <<   n ;     }   }   