#include <vector>

#include <cstdlib>

#include <algorithm>

#include <iostream>

using namespace std;

int main() {

	int N, M;

	cin >> N >> M;

	vector<pair<int, int>> vec;

	for (int i = 0; i < M ;i++) {

		int a, b, k;

		cin >> a >> b >> k;

		vec.push_back(make_pair(a, k));

		vec.push_back(make_pair(b + 1, -k));

	}

    sort(vec.begin(), vec.end());

    long long max_val = 0;

    long long cur_val = 0;

    for (int i = 0; i < M * 2; i++) {

        cur_val += vec[i].second;

        max_val = max(max_val, cur_val);

    }

	cout << max_val << endl;

    return 0;

}