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

#define MAX 1024

using namespace std;

int n, m;
int pr[3][MAX];
int cond[MAX], val[MAX];

inline int probeaza(int ind)
{
	if (cond[ind] == 0)
		return (val[pr[0][ind]] | val[pr[1][ind]]);
	if (cond[ind] == 3)
		return ((!val[pr[0][ind]]) | (!val[pr[1][ind]]));
	return (val[pr[0][ind]] | (!val[pr[1][ind]]));
}

int main()
{
	srand(time(0));
	freopen("party.in", "r", stdin);
	freopen("party.out", "w", stdout);

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

	for (int i = 1; i <= m; i++)
	{
		scanf("%d %d %d", &pr[0][i], &pr[1][i], &cond[i]);

		if (cond[i] == 2)
		{
			swap(pr[0][i], pr[1][i]);
			cond[i] = 1;
		}
	}

	for (int i = 1; i <= n; i++)
		val[i] = 1;

	for (int ok = 0; !ok; )
	{
		ok = 1;
		for (int i = 1; i <= m; i++)
			if (!probeaza(i))
			{
				ok = 0;
				
				int sch = rand() % 2;
				val[pr[sch][i]] ^= 1;
			}
	}

	int nr = 0;
	for (int i = 1; i <= n; i++)
		nr += val[i];

	printf("%d\n", nr);
	for (int i = 1; i <= n; i++)
		if (val[i])
			printf("%d\n", i);

	fclose(stdin);
	fclose(stdout);
	return 0;
}