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

template <typename T>
ostream &operator<<(ostream &os, const vector<T> &vec)
{
    os << "{";
    if (!vec.empty())
        os << vec[0];
    for (int i = 1; i < vec.size(); i++)
        os << ", " << vec[i];
    os << "}";

    return os;
}

int n, m;

struct Event{
    int time;
    int color;
    int delta;
};

vector<Event> events;
vector<Event>::iterator it;
int state[3];

int main()
{
    #if IOSTREAM_BOOST
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    #endif
    
    cin >> n >> m;
    events.resize(m);
    

    for(int i = 0; i < m; i++){
        int a, b, c;
        cin >> a >> b >> c;
        a--, c--;
        events.push_back(Event({a, c, 1}));
        events.push_back(Event({b, c, -1}));
    }

    sort(events.begin(), events.end(), [](Event &a, Event &b){
        return a.time < b.time;
    });

    it = events.begin();
    int counter = 0;
    for(int i = 0; i < n; i++){
        while(it != events.end() && it->time == i) state[it->color] += it->delta, it++;
        //cout << i << " " << state[0] << " " << state[1] << " " << state[2] << "\n";
        if(state[0] && state[1] && !state[2]) counter++;
    }
    cout << counter << "\n";

    return 0;
}