#include <stdio.h>
#include <stdlib.h>
#include <time.h>



struct vector
{
 int x,y,z;
}v[101*10];

char use[101];

int main()
{
 int i,pos,N,M,end,ok;

 freopen("party.in","r",stdin);

 scanf("%d%d",&N,&M);
 for(i=1;i<=M;i++) scanf("%d%d%d",&v[i].x,&v[i].y,&v[i].z);

 srand(time(NULL));
 for(i=1;i<=N;i++) use[i]=rand()%2;

 end=0;
 while(!end)
 {
  end=1;
  pos=rand()%M+1;

  for(i=pos;i<=M;i++)
   if(v[i].z==0)
   {
    if(use[v[i].x]==0&&use[v[i].y]==0)
    {
     ok=rand()%2;
     if(ok) use[v[i].x]=1-use[v[i].x];
     else use[v[i].y]=1-use[v[i].y];
     end=0;
     break;
    }
   }
   else
   if(v[i].z==1)
   {
    if(use[v[i].x]==0&&use[v[i].y]!=0)
    {
     ok=rand()%2;
     if(ok) use[v[i].x]=1-use[v[i].x];
     else use[v[i].y]=1-use[v[i].y];
     end=0;
     break;
    }
   }
   else
   if(v[i].z==2)
   {
    if(use[v[i].x]!=0&&use[v[i].y]==0)
    {
     ok=rand()%2;
     if(ok) use[v[i].x]=1-use[v[i].x];
     else use[v[i].y]=1-use[v[i].y];
     end=0;
     break;
    }
   }
   else
   if(v[i].z==3)
   {
    if(use[v[i].x]==1&&use[v[i].y]==1)
    {
     ok=rand()%2;
     if(ok) use[v[i].x]=1-use[v[i].x];
     else use[v[i].y]=1-use[v[i].y];
     end=0;
     break;
    }
   }

  if(end)
   for(i=1;i<=pos;i++)
    if(v[i].z==0)
    {
     if(use[v[i].x]==0&&use[v[i].y]==0)
     {
      ok=rand()%2;
      if(ok) use[v[i].x]=1-use[v[i].x];
      else use[v[i].y]=1-use[v[i].y];
      end=0;
      break;
     }
    }
    else
    if(v[i].z==1)
    {
     if(use[v[i].x]==0&&use[v[i].y]!=0)
     {
      ok=rand()%2;
      if(ok) use[v[i].x]=1-use[v[i].x];
      else use[v[i].y]=1-use[v[i].y];
      end=0;
      break;
     }
    }
    else
    if(v[i].z==2)
    {
     if(use[v[i].x]!=0&&use[v[i].y]==0)
     {
      ok=rand()%2;
      if(ok) use[v[i].x]=1-use[v[i].x];
      else use[v[i].y]=1-use[v[i].y];
      end=0;
      break;
     }
    }
    else
    if(v[i].z==3)
    {
     if(use[v[i].x]==1&&use[v[i].y]==1)
     {
      ok=rand()%2;
      if(ok) use[v[i].x]=1-use[v[i].x];
      else use[v[i].y]=1-use[v[i].y];
      end=0;
      break;
     }
    }
 }

 freopen("party.out","w",stdout);

 use[0]=0;
 for(i=1;i<=N;i++) use[0]+=use[i];

 printf("%d\n",use[0]);

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

 return 0;
}