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#include <bits/stdc++.h>

using namespace std;

#define PB push_back
#define SZ(x) int((x).size())
#define REP(i, n) for (int i = 0, _ = (n); i < _; ++i)
#define FOR(i, a, b) for (int i = (a), _ = (b); i <= _; ++i)
#define FORD(i, a, b) for (int i = (a), _ = (b); i >= _; --i)

#ifdef DEBUG
#define DEB(x) (cerr << x)
#else
#define DEB(x)
#endif

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

const int INF = 1e9 + 9;
const int MAX_N = 1e6 + 1;

struct Event {
    int position;
    int value;
    int color;

    bool operator<(const Event &other) const {
        if (position != other.position) {
            return position < other.position;
        }
        return value > other.value;
    }
};

int counter[4] = {};
vector<Event> events;

void inline one() {
    int n, m;
    cin >> n >> m;
    while (m--) {
        int left, right, color;
        cin >> left >> right >> color;
        events.PB((Event){left, +1, color});
        events.PB((Event){right, -1, color});
    }
    sort(events.begin(), events.end());
    int result = 0;
    int last_processed = 0;
    for (auto const &event : events) {
        DEB("event: pos=" << event.position << " value=" << event.value << " color=" << event.color << "\n");
        DEB("before: " << counter[1] << ", " << counter[2] << ", " << counter[3] << "\n");
        if (event.value > 0) {
            if (counter[1] and counter[2] and (not counter[3])) {
                int len = event.position - last_processed - 1;
                DEB("result1 += " << len << "\n");
                result += len;
            }
            counter[event.color] += event.value;
            last_processed = event.position - 1;
        } else {
            if (counter[1] and counter[2] and (not counter[3])) {
                int len = event.position - last_processed;
                DEB("result2 += " << len << "\n");
                result += len;
            }
            counter[event.color] += event.value;
            last_processed = event.position;
        }
        DEB("after: " << counter[1] << ", " << counter[2] << ", " << counter[3] << "\n");
    }
    cout << result << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    // int z; cin >> z; while(z--)
    one();
}