//2 SAT
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

using namespace std;

int n, m;

int x[1001], y[1001], tip[1001];
int use[101];


inline bool isOk (int i)
{
	if (tip[i] == 0)
	{
		return (use[x[i]] || use[y[i]]);
	}

	if (tip[i] == 1)
	{
		return (use[x[i]] ||  !use[y[i]]);
			
	}

	if (tip[i] == 2)
	{
		return (use[y[i]] ||  !use[x[i]]);

	}

	if (tip[i] == 3)
	{
		return (!use[x[i]]   || !use[y[i]]);
	}


	return false;

}
void solve ()
{
	int ok = 1;

	int i, j;

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

	while (ok)
	{
		ok = 0;
		for (i = 1; i <= m; ++i)
			if (isOk (i) == false)
			{
				ok = 1;
				int p = rand () & 1;
				if (p)
					use[x[i]] ^= 1;
				else
					use[y[i]] ^= 1;
			}
		
	}

	int nr = 0;

	for (i = 1; i <= n; ++i)
		if (use[i])
			++nr;

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


}


int main ()
{
	srand (time (0));

	freopen ("party.in", "r", stdin);
	freopen ("party.out", "w", stdout);

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

	int i;

	for (i = 1; i <= m; ++i)
		scanf ("%d %d %d\n", &x[i], &y[i], &tip[i]);

	solve ();


	return 0;
}