#include <fstream>
//#include <iostream>
#include <vector>
#include <stack>

using namespace std;

ifstream cin("party.in");
ofstream cout("party.out");

const int NMAX = 200;

int N, M;
vector <int> g[NMAX + 5];
vector <int> t[NMAX + 5];

bool seen[NMAX + 5];
stack <int> st;
void dfs1(int node)
{
	seen[node] = true;

	for(auto it : g[node])
		if(!seen[it]) dfs1(it);

	st.push(node);
}

int kComp;
int comp[NMAX + 5];
void dfs2(int node)
{
	comp[node] = kComp;

	for(auto it : t[node])
		if(comp[it] == 0) dfs2(it);
}

vector <int> sol;

int Not(int x)
{
	return x;
}

int Nrm(int x)
{
	return x + N;
}

int main()
{
	cin >> N >> M;

	for(int i = 1; i <= M; i++)
		{
			int x, y, z;
			cin >> x >> y >> z;

			if(z == 0)
				{	
					g[Not(x)].push_back(Nrm(y));
					g[Not(y)].push_back(Nrm(x));

					t[Nrm(y)].push_back(Not(x));
					t[Nrm(x)].push_back(Not(y));
				}
			else if(z == 1)
				{
					g[Not(x)].push_back(Not(y));
					g[Nrm(y)].push_back(Nrm(x));

					t[Not(y)].push_back(Not(x));
					t[Nrm(x)].push_back(Nrm(y));
				}
			else if(z == 2)
				{
					g[Nrm(x)].push_back(Nrm(y));
					g[Not(y)].push_back(Not(x));

					t[Nrm(y)].push_back(Nrm(x));
					t[Not(x)].push_back(Not(y));
				}	
			else
				{
					g[Nrm(x)].push_back(Not(y));
					g[Nrm(y)].push_back(Not(x));

					t[Not(y)].push_back(Nrm(x));
					t[Not(x)].push_back(Nrm(y));
				}
		}

	for(int i = 1; i <= 2 * N; i++)
		if(!seen[i]) dfs1(i);

	while(!st.empty())
	{
		int node = st.top(); st.pop();

		if(comp[node] == 0)
		{
			++kComp;
			dfs2(node);
		}
	}

	for(int i = 1; i <= N; i++)
		if(comp[i + N] > comp[i])
			sol.push_back(i);

	cout << sol.size() << '\n';
	for(auto it : sol)
		cout << it << '\n';

	return 0;
}