#include <iostream>
#include <algorithm>
using namespace std;
int l[30005], ans;
struct sug {
    int b, e, t;
} su[5005];
bool cmp(sug a, sug b) {
    return a.e < b.e;
}
int main() {
    int n, h;
    cin >> n >> h;

    for (int i = 1; i <= h; i++) {
        cin >> su[i].b >> su[i].e >> su[i].t;
    }

    sort(su + 1, su + 1 + h, cmp);

    for (int i = 1; i <= h; i++) {
        int ant = 0;

        for (int j = su[i].e; j >= su[i].b; j--) {
            if (l[j] == 1)
                ant++;
        }

        for (int j = su[i].e; j >= su[i].b; j--) {
            if (ant >= su[i].t)
                break;

            if (l[j] == 1)
                continue;

            l[j] = 1;
            ans++;
            ant++;
        }
    }

    cout << ans;
    return 0;
}