#include <fstream>
using namespace std;
ifstream cin("party.in");
ofstream cout("party.out");
struct cerinta {
    int x, y, z;
    }A[1024];
int P[128];
int N, M, ok, i, X, Y, Z, Cnt;
int main()
{   cin>>N>>M;
    for(i=1;i<=N;i++)P[i]=1;
    for(i=1;i<=M;i++)cin>>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])Cnt++;
    cout<<Cnt<<endl;
    for(i=1;i<=N;i++)
    if(P[i])cout<<i<<endl;
    return 0;
}