#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
const int nmax=105;
vector<int> v[nmax];
bool viz[nmax],val[nmax],ap[nmax];
int r[nmax];
int i,j,n,x,m,tip,y,k,nr;
inline int no(int x)
{
    if(x<=n) return n+x;
    return x-n;
}
void dfs(int x)
{
    viz[x]=1;
   for(int i=0;i<v[x].size();i++)
     if(!viz[v[x][i]])
        dfs(v[x][i]);
    k++;r[k]=x;
}
int main()
{
    ifstream f("party.in");
    ofstream g("party.out");
    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>x>>y>>tip;
        if(tip==0)
        {
            //x sau y
            v[no(x)].push_back(y);
            //vt[y].push_back(no(x));
            v[no(y)].push_back(x);
            //vt[x].push_back(no(y));
        }
        if(tip==1)
        {
            //x sau !y
            v[no(x)].push_back(no(y));
            //vt[no(y)].push_back(no(x));
            v[y].push_back(x);
            //vt[x].push_back(y);
        }
        if(tip==2)
        {
            // !x sau y
            v[x].push_back(y);
            //vt[y].push_back(x);
            v[no(y)].push_back(no(x));
            //vt[no(x)].push_back(no(y));
        }
        if(tip==3)
        {
            // !x sau !y
            v[x].push_back(no(y));
            //vt[no(y)].push_back(x);
            v[y].push_back(no(x));
            //vt[no(x)].push_back(y);
        }
    }
    for(i=1;i<=2*n;i++)
        if(!viz[i])
        dfs(i);
    for(i=2*n;i>=1;i--)
    {
        x=r[i];
        ap[x]=1;
        if(ap[no(x)]==1) val[x]=1;
        else val[x]=0;
        if(val[x]&&x<=n)
            nr++;
    }
    g<<nr<<'\n';
    for(i=1;i<=n;i++)
        if(val[i])
            g<<i<<'\n';
    return 0;
}