#include<stdio.h>
#include<vector>
#include<stack>

using namespace std;

#define NMAX 256
#define pb push_back

vector< int > G[NMAX],GT[NMAX];
stack< int > Q;
bool viz[NMAX],SOL[NMAX];
int N,M,ANS;

inline int not( int value )
{
	return value<=N ? value+N : value-N;
}

inline void push_edge( int node1, int node2 )
{
	G[node1].pb( node2 );
	GT[node2].pb( node1 );
}

void DF1( int node )
{
	viz[node]=1;

	int i,v;
	for(i=0; i<G[node].size(); ++i)
	{
		v=G[node][i];
		if( !viz[v] )
			DF1(v);
	}

	Q.push( node );
}

void DF2( int node )
{
	viz[node]=0;
	SOL[ not(node) ]=1;
	SOL[node]=0;

	int i,v;
	for(i=0; i<GT[node].size(); ++i)
	{
		v=GT[node][i];
		if( viz[v] )
			DF2(v);
	}
}

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

	scanf("%d%d",&N,&M);
	
	int i,a1,a2,a3;
	for(i=1; i<=M; ++i)
	{
		scanf("%d%d%d",&a1,&a2,&a3);
		switch( a3 )
		{
			case 0:
			{
					push_edge( not(a1), a2 );
					push_edge( not(a2), a1 );
					break;
			}
			case 1: 
			{
					push_edge( not(a1), not(a2) ); 
					push_edge( a2, a1 );
					break;
			}
			case 2:
			{
					push_edge( not(a2), not(a1) );
					push_edge( a1, a2 );
					break;
			}
			case 3:
			{		
					push_edge( a1, not(a2) );
					push_edge( a2, not(a1) ); 
					break;
			}
		}
	}

	for(i=1; i<=(N<<1); ++i)
	{
		if( !viz[i] )
			DF1( i );
	}

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

		if( viz[node] && viz[ not(node) ] )
			DF2( node );
	}

	for(i=1; i<=N; ++i)
		ANS+=SOL[i];

	printf("%d\n",ANS);
	
	for(i=1; i<=N; ++i)
		if( SOL[i] )
			printf("%d\n",i);

	return 0;
}