#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;
}