#include <fstream>
#include <utility>
#include <stdlib.h>
#include <vector>
using namespace std;
#define maxn 1001
#define FOR(i,a,b) for (i = (a); i <= (b); i++)
#define sz size()
#define pb push_back
#define mp make_pair
#define s second
#define f first
int N, M, bad;
int v[maxn], c[maxn];
vector<pair<int, int> > exp;

int eval(int pos)
{
	pair<int, int> e = exp[pos];
	if (c[pos] == 0)
		return (v[e.f] || v[e.s]);
	if (c[pos] == 1)
		return (v[e.f] || !v[e.s]);
	if (c[pos] == 2)
		return (!v[e.f] || v[e.s]);
	if (c[pos] == 3)
		return (!v[e.f] || !v[e.s]);
}

int extra()
{
	int i;
	FOR(i, 1, N)
		if (v[i]) return 1;
	return 0;
}

int main()
{
	int i, x, y, pas;
	ifstream fin("party.in");
	ofstream fout("party.out");
	fin >> N >> M;
	FOR(i, 0, M - 1)
	{
		fin >> x >> y >> c[i];
		exp.pb(mp(x, y));
	}

/*	FOR(i, 0, M - 1)
		fout << exp[i].f << " " <<  exp[i].s << " " << c[i] << '\n';*/
		
	FOR(pas, 0, 10000)
	{
		int ok = eval(0);
		if (!eval(0)) bad = 0;
		FOR(i, 1, M - 1)
		{
			ok = ok && eval(i);
			if (!eval(i)) bad = i;
		}

		if (ok && extra()) break;
		v[exp[bad].f] = !v[exp[bad].f];
	}

	int res = 0;
	for (i = 1; i <= N; i++)
		if (v[i]) res++;
	fout << res << '\n';
	FOR(i, 1, N)
		if (v[i]) fout << i << '\n';
	fin.close(), fout.close();
}