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

int baza = 1;

short D[3000000];

void Z(int v, int p, int k, int pz, int kz, int w)
{
    if(k < pz || p > kz)
    {
        return;
    }

    if(pz <= p && k <= kz)
    {
        D[v] |= w;
        return;
    }

    Z(2 * v, p, (p + k) / 2, pz, kz, w);
    Z((2 * v) + 1, ((p + k) / 2) + 1, k, pz, kz, w);

    return;
}

short w;

short Q(int v)
{
    v += baza;

    w = 0;

    while(v > 0)
    {
        w |= D[v];
        v /= 2;
    }

    return w;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int a, b;
    cin >> a >> b;

    while(baza < a)
    {
        baza *= 2;
    }

    int c, d, e;

    for(int i = 0; i < b; i++)
    {
        cin >> c >> d >> e;
        Z(1, 1, baza, c, d, (1 << (e - 1)));
    }

    int wyn = 0;

    for(int i = 0; i < a; i++)
    {
        wyn += (Q(i) == 3);
    }

    cout << wyn << endl;

    return 0;
}