#include <fstream>
using namespace std;
ifstream f ("party.in");
ofstream g ("party.out");
struct
{
    int x,y,z;
}v[1031];
int p[131];
int n,m,ok,i,X,Y,Z,nr;
int main()
{
    f>>n>>m;
    for(i=1;i<=n;++i) p[i]=1;
    for(i=1;i<=m;++i) f>>v[i].x>>v[i].y>>v[i].z;
    ok=0;
    while(!ok) //cat timp nu respecta toate cerintele
    {
        ok=1;
        for(i=1;i<=m;++i)
        {
            X=v[i].x; Y=v[i].y; Z=v[i].z;
            if(Z==0) if(p[X]==0&&p[Y]==0) {p[X]=1;p[Y]=1;ok=0;break;} //schimbam convenabil astfel in cat sa respecte fiecare cerinta
            if(Z==1) if(p[X]==0&&p[Y]!=0) {p[Y]=0;ok=0;break;}
            if(Z==2) if(p[Y]==0&&p[X]!=0) {p[X]=0;ok=0;break;}
            if(Z==3) if(p[X]==1&&p[Y]==1) {p[Y]=0;ok=0;break;}
        }
    }
    for(i=1;i<=n;i++) if(p[i]) nr++; //numaram cati prieteni mai avem
    g<<nr<<'\n';
    for(i=1;i<=n;++i) if(p[i]) g<<i<<'\n'; //afisam prietenii
    return 0;
}