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

using namespace std;
vector< int > G[256],GT[256];
stack< int > Q;
bool viz[256],SOL[256];
int N,M,ANS;

inline int mnot( int value )
{
 return value<=N ? value+N : value-N;
}

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

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

 unsigned 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[ mnot(node) ]=1;
 SOL[node]=0;

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

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

 assert( scanf("%d%d",&N,&M)!=EOF );

 int i,a1,a2,a3;
 for(i=1; i<=M; ++i)
 {
  assert( scanf("%d%d%d",&a1,&a2,&a3)!=EOF );
  switch( a3 )
  {
   case 0:
   {
     push_edge( mnot(a1), a2 );
     push_edge( mnot(a2), a1 );
     break;
   }
   case 1:
   {
     push_edge( mnot(a1), mnot(a2) );
     push_edge( a2, a1 );
     break;
   }
   case 2:
   {
     push_edge( mnot(a2), mnot(a1) );
     push_edge( a1, a2 );
     break;
   }
   case 3:
   {
     push_edge( a1, mnot(a2) );
     push_edge( a2, mnot(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[ mnot(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;
}