#include<fstream>
using namespace std;
ifstream fi("party.in");
ofstream fo("party.out");
int N, M;
int x[1000], E[1000][2];
int i,v;
int modul(int a)
{
	if (a < 0) return - a;
	return a;
}
int main()
{
	fi >> N >> M;
	for (i = 1; i <= M; i++)
	{
		int a;
		fi >> E[i][0] >> E[i][1];
		fi >> a;
		if (a == 1) E[i][1] = -E[i][1];
		if (a == 2) E[i][0] = -E[i][0];
		if (a == 3) {E[i][1] = -E[i][1]; E[i][0] = -E[i][0];}

	}
	for (i = 1; i <= N; i++)
		x[i] = rand() % 2;
	while(1)
	{
		//verificam daca propozitiile sunt adevarate
		for (i = 1; i <= M; i++)
		{
			if (E[i][0] > 0 && E[i][1] > 0) v = x[E[i][0]] | x[E[i][1]];
			if (E[i][0] > 0 && E[i][1] < 0) v = x[E[i][0]] | (1-x[-E[i][1]]);
			if (E[i][0] < 0 && E[i][1] > 0) v = (1-x[-E[i][0]]) | x[E[i][1]];
			if (E[i][0] < 0 && E[i][1] < 0) v = (1-x[-E[i][0]]) | (1-x[-E[i][1]]);
			if (v==0) break;
		}
		int var;
		if (!v) 
		{
			var = rand() % 2;
			x[modul(E[i][var])] = 1 - x[modul(E[i][var])];
		}
		else break;
	}
	int rez = 0;
	for (i = 1; i <= N; i++) rez += x[i];
	fo << rez<<'\n';
	for (i = 1; i <= N; i++) if (x[i]) fo << i << '\n';
	fi.close();
	fo.close();
	return 0;
}