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#include <stdio.h>
#include <vector>
#include<algorithm>

using namespace std;

struct Op
{
	int pos;
	int color;
	bool added;
};


struct less_than_key
{
	inline bool operator() (const Op& struct1, const Op& struct2)
	{
		return (struct1.pos < struct2.pos);
	}
};

int main()
{
	int n, m, h = 0;

	scanf("%d %d", &n, &m);

	vector<Op> ops(2 * m);
	for (int i = 0; i < m; i++)
	{
		int l, r, k;
		scanf("%d %d %d", &l, &r, &k);

		ops[2 * i].added = true;
		ops[2 * i].color = k;
		ops[2 * i].pos = l;
		ops[2 * i + 1].added = false;
		ops[2 * i + 1].color = k;
		ops[2 * i + 1].pos = r + 1;
	}

	sort(ops.begin(), ops.end(), less_than_key());

	int r = 0, y = 0, b = 0, last_pos = 0, sum = 0;

	for (int i = 0; i < 2 * m;)
	{
		int cur_pos = ops[i].pos;
		if (r == 0 && y > 0 && b > 0)
		{
			sum += cur_pos - last_pos;
		}
		last_pos = cur_pos;
		while (i < 2 * m && ops[i].pos == cur_pos)
		{
			int f = ops[i].added ? 1 : -1;

			if (ops[i].color == 1)
			{
				y += f;
			}
			else if (ops[i].color == 2)
			{
				b += f;
			}
			else if (ops[i].color == 3)
			{
				r += f;
			}

			i++;
		}
	}

	printf("%d", sum);
}