#include <fstream>

using namespace std;

struct cerinta {
    int x, y, z;}
    a[1100];
int v[150];
int N,k, M, ok, i, X, Y, Z ;
    ifstream fin("party.in");
    ofstream fout("party.out");
int main()
{

fin>>N>>M;
    for(i=1;i<=N;i++)v[i]=1;
      for(i=1;i<=M;i++)fin>>a[i].x>>a[i].y>>a[i].z; ok=0;

    while(ok==0){
    ok=1;
    for (i=1;i<=M;i++){
      X=a[i].x, Y=a[i].y, Z=a[i].z;
      if(Z==0)
       if(v[X]==0 && v[Y]==0){v[X]=1;v[Y]=1;ok=0;break;}
        if(Z==1)
         if(v[X]==0 && v[Y]!=0){v[Y]=0;ok=0;break;}
          if(Z==2)
           if(v[Y]==0 && v[X]!=0){v[X]=0;ok=0;break;}
            if(Z==3)
             if(v[X]==1 && v[Y]==1){v[Y]=0;ok=0;break;}
            }
}
    for(i=1;i<=N;i++)
       if(v[i])k++;
         fout<<k<<'\n';
    for(i=1;i<=N;i++)
       if(v[i])
       fout<<i<<'\n';
            return 0;
}