#include <cstdio>
#include <cstring>
#include <fstream>
#include <algorithm>
#include <utility>

using namespace std;

int N, M;
pair<int, int> term[1002];
int type[1002];

bool go[102], sett[102];
bool newgo[102], newset[102];

int main()
{
	ifstream fin("party.in");
	ofstream fout("party.out");
	
	fin >> N >> M;
	for (int i = 1; i <= M; ++i)
		fin >> term[i].first >> term[i].second >> type[i];
	
	for (int i = 1; i <= N; ++i)
		if (!sett[i])
		{
			sett[i] = true, go[i] = true;
			
			// verify
			
			memcpy(newgo, go, sizeof(newgo));
			memcpy(newset, sett, sizeof(newset));
			
			bool ok = true, valid = true;
			while (ok && valid)
			{
				ok = false;
				for (int j = 1; j <= M; ++j)
					if (newset[term[j].first] ^ newset[term[j].second])
					{
						int f1 = term[j].first, f2 = term[j].second;
						if (newset[term[j].second])
							swap(f1, f2);
						
						if (newset[f1] && !newgo[f1])
							if (type[j] == 0 || type[j] == 1)
							{
								newset[f2] = true;
								if (type[j] == 0)
									newgo[f2] = true;
								else if (type[j] == 1)
									newgo[f2] = false;

								ok = true;
							}
						if (newset[f1] && newgo[f1])
							if (type[j] == 2 || type[j] == 3)
							{
								newset[f2] = true;
								if (type[j] == 2)
									newgo[f2] = true;
								else if (type[j] == 3)
									newgo[f2] = false;

								ok = true;
							}
					}
					else if (newset[term[j].first] && newset[term[j].second])
					{
						if (type[j] == 0 && !newgo[term[j].first] && !newgo[term[j].second]) valid = false;
						if (type[j] == 1 && !newgo[term[j].first] && newgo[term[j].second]) valid = false;
						if (type[j] == 2 && newgo[term[j].first] && !newgo[term[j].second]) valid = false;
						if (type[j] == 3 && newgo[term[j].first] && newgo[term[j].second]) valid = false;
					}
			}
			
			if (valid)
			{
				memcpy(go, newgo, sizeof(go));
				memcpy(sett, newset, sizeof(sett));
			}
			else
				go[i] = false;
			
			ok = true;
			while (ok)
			{
				ok = false;
				for (int j = 1; j <= M; ++j)
					if (newset[term[j].first] ^ newset[term[j].second])
					{
						int f1 = term[j].first, f2 = term[j].second;
						if (newset[term[j].second])
							swap(f1, f2);
						
						if (newset[f1] && !newgo[f1])
							if (type[j] == 0 || type[j] == 1)
							{
								newset[f2] = true;
								if (type[j] == 0)
									newgo[f2] = true;
								else if (type[j] == 1)
									newgo[f2] = false;

								ok = true;
							}
						if (newset[f1] && newgo[f1])
							if (type[j] == 2 || type[j] == 3)
							{
								newset[f2] = true;
								if (type[j] == 2)
									newgo[f2] = true;
								else if (type[j] == 3)
									newgo[f2] = false;

								ok = true;
							}
					}
			}
		}
	
	int result = 0;
	for (int i = 1; i <= N; ++i)
		result += go[i];
	
	fout << result << '\n';
	for (int i = 1; i <= N; ++i)
		if (go[i])
			fout << i << '\n';
	
	fin.close();
	fout.close();
}