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#include <iostream>
#include <vector>
#include <utility>
#include <algorithm>

using namespace std;

int main() {
	ios_base::sync_with_stdio(0);

	int N, M;
	cin >> N >> M;

	typedef pair<int, int> Event;
	vector<Event> starts;
	vector<Event> ends;

	starts.reserve(M);
	ends.reserve(M);

	int colors[] = {0,0,0};
	enum { Y, B, R };

	auto isGreen = [&colors]() { return colors[Y] > 0 & colors[B] > 0 && colors[R] == 0; };

	for (int i = 0; i < M; i++) {
		int l, r, k;
		cin >> l >> r >> k;

		starts.push_back(Event(l-1, k-1));
		ends.push_back(Event(r, k-1));
	}
	sort(starts.begin(), starts.end());
	sort(ends.begin(), ends.end());

	int s = 0, e = 0;
	int prev = 0;
	int res = 0;

	auto update = [&res, &prev, &isGreen](int val) {
		if (val != prev) {
			if (isGreen())
				res += val - prev;
			prev = val;
		}
	};

	while (s < starts.size() || e < ends.size()) {
		if (s < starts.size() && starts[s].first <= ends[e].first) {
			update(starts[s].first);
			colors[starts[s].second]++;
			s++;
		} else {
			update(ends[e].first);
			colors[ends[e].second]--;
			e++;
		}
	}
	cout << res << endl;

	return 0;
}