#include <algorithm>
#include <cstdio>
#include <iostream>
#include <utility>

using namespace std;

int n;
int h;
pair<pair<int, int>, int> house[5114];
// e b t
bool tree[31145];
int res;

int main () {

	freopen ("plant_tree.in", "r", stdin);
	freopen ("plant_tree.out", "w", stdout);
	
	cin >> n >> h;
	for (int i = 1; i <= h; i++) {
	    cin >> house[i].first.second >> house[i].first.first >> house[i].second;
    }
    sort (house + 1, house + 1 + h);
    
    for (int i = 1; i <= h; i++) {
        int cc = 0;
        for (int j = house[i].first.second; j <= house[i].first.first; j++) {
            cc += tree[j];
        }
        if (cc >= house[i].second) {
            continue;
        }
        for (int j = house[i].first.first, k = house[i].second - cc; k; j--) {
            if (!tree[j]) {
                tree[j] = true;
                k--;
                res++;
            }
        }
    }
    
    cout << res << endl;

	return 0;
}