#include <algorithm>
#include <cmath>
#include <cstdio>
#include <iostream>

using namespace std;

const int N = 114514;

struct pancake {
	int t;
	int p;
	int v;

	bool operator< (pancake other) {
		return t < other.t;
	}
};

int n;
int w;
pancake nums[N];
int dp[N];
int res;

void ParseIn () {
	
	freopen ("free.in", "r" ,stdin);
	freopen ("free.out", "w", stdout);

	cin >> w >> n;
	for (int i = 1; i <= n; i++) {
		cin >> nums[i].t >> nums[i].p >> nums[i].v;
	}
	sort (nums + 1, nums + 1 + n);
	
}

void Core () {
	
	for (int i = 1; i <= n; i++) {
		dp[i] = nums[i].v;
		for (int j = 1; j < i; j++) {
			if (nums[i].t - nums[j].t >= abs (nums[i].p - nums[j].p)) {
				dp[i] = max (dp[i], dp[j] + nums[i].v);
			}
		}
		res = max (res, dp[i]);
	}
	
}

void CWriteOut () {
	
	cout << res << endl;
	
}

int main () {
	
	ParseIn ();
	Core ();
	CWriteOut ();
	
	return 0;
}