#include <bits/stdc++.h>
using namespace std;

int n, m, ans = 0;

struct line
{
    int s, e, v;
}a[100005];

bool used[3000005];
bool cmp(line x, line y)
{
    return x.e < y.e;
}

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= m; i++) cin >> a[i].s >> a[i].e >> a[i].v;
    sort (a + 1, a + m + 1, cmp);
    for (int i = 1; i <= m; i++)
    {
        int k = 0;
        for (int j = a[i].s; j <= a[i].e; j++) 
        {
            if (used[j]) k++;
        }
        if (k >= a[i].v) continue;
        for (int j = a[i].e; j >= a[i].s; j--)
        {
            if (!used[j])
            {
                used[j] = 1;
                k++;
                ans++;
                if (k == a[i].v) break;
            }
        }
    }
    cout << ans << endl;
    return 0;
}