#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
#define MAX 205

ifstream fin("party.in");
ofstream fout("party.out");

typedef vector <int> :: iterator iter;
vector <int> G[MAX];

int viz[MAX], st[MAX], rez[MAX];

void df(int nod)
{
    viz[nod]=1;
    for(iter it=G[nod].begin();it!=G[nod].end();it++)
    {
        if(!viz[*it])
            df(*it);
    }


    st[++st[0]]=nod-100;
}

int main()
{
    int n, m, x, y, t, i;
    fin>>n>>m;
    while(m--)
    {
        fin>>x>>y>>t;
        if(t==1 || t==3)
            y=-y;
        if(t==2 || t==3)
            x=-x;
        G[-x+100].push_back(y+100);
        G[-y+100].push_back(x+100);
    }
    for(i=-n;i<=n;i++)
    {
        if(i)
        {
            if(!viz[i+100])
                df(i+100);
        }
    }
    for(i=2*n;i>=1;i--)
    {
        if(!rez[st[i]+100] && !rez[-st[i]+100])
        {
            rez[-st[i]+100]=1;
        }
    }
    int s=0;
    for(i=1;i<=n;i++)
    {
        if(rez[i+100])
            s++;
    }
    fout << s << "\n";
    for(i=1;i<=n;i++)
    {
        if(rez[i+100])
            fout << i << "\n";
    }
}