#include <fstream>

using namespace std;

struct cerinta {
    int x, y, z;
    }A[1024];
int P[128];
int n, m, ok, i, X, Y, Z, k;
int main()
{
    ifstream fin("party.in");
    ofstream fout("party.out");
    fin>>n>>m;
    for(i=1;i<=n;i++)
        P[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(P[X]==0 && P[Y]==0)
    {P[X]=1;P[Y]=1;ok=0;break;}
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])k++;
    fout<<k<<endl;
    for(i=1;i<=n;i++)
    if(P[i])fout<<i<<endl;

}