#include <cstdio>
#include <vector>
#include <algorithm>
#define Nmax 505

using namespace std;

vector <int> L[Nmax],T[Nmax];
int Sorted[Nmax],len,sol[Nmax],n;
bool viz[Nmax];

inline int non(int x)
{
    if(x>n) return x-n;
    return x+n;
}

inline void Dfs(int nod)
{
    viz[nod]=true;
    vector <int> ::iterator it;
    for(it=L[nod].begin();it!=L[nod].end();++it)
        if(!viz[*it]) Dfs(*it);
    Sorted[++len]=nod;
}

inline void Dfs2(int nod)
{
    viz[nod]=false; sol[nod]=0; sol[non(nod)]=1;
    vector <int> ::iterator it;
    for(it=T[nod].begin();it!=T[nod].end();++it)
        if(viz[*it]) Dfs2(*it);

}

int main()
{
    int m,x,y,tip,i,cnt;
    freopen ("party.in","r",stdin);
    freopen ("party.out","w",stdout);
    scanf("%d%d", &n,&m);
    while(m--)
    {
        scanf("%d%d%d", &x,&y,&tip);
        if(!tip)
        {
            L[non(x)].push_back(y);
            L[non(y)].push_back(x);
            T[y].push_back(non(x));
            T[x].push_back(non(y));
        }
        else
            if(tip==1)
            {
                L[y].push_back(x);
                T[x].push_back(y);
            }
            else
                if(tip==2)
                {
                    L[x].push_back(y);
                    T[y].push_back(x);
                }
                else
                {
                    L[y].push_back(non(x));
                    L[x].push_back(non(y));
                    T[non(x)].push_back(y);
                    T[non(y)].push_back(x);
                }
    }
    for(i=1;i<=2*n;++i)
        if(!viz[i]) Dfs(i);
    reverse(Sorted+1,Sorted+len+1);
    for(i=1;i<=len;++i)
        if(viz[Sorted[i]] && viz[non(Sorted[i])]) Dfs2(Sorted[i]);
    for(i=1,cnt=0;i<=n;++i) cnt+=(sol[i]==1);
    printf("%d\n", cnt);
    for(i=1;i<=n;++i)
        if(sol[i]) printf("%d\n", i);
    return 0;
}