#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

vector < vector < int > > lv,lv2;
vector <int> noduri,v,f,plus,minus;
int n,m,i,j,pas,ct=0;

int neg(int x)
{
    if (x<=n)
        return x+n;
    else
        return x-n;
}

void citire()
{
    int a,b,t;
    scanf("%d%d\n",&n,&m);
    lv.resize(2*n+1);
    for (i=0;i<m;i++)
    {
        scanf("%d %d %d\n",&a,&b,&t);
        if (t==0)
        {
            lv[neg(a)].push_back(b);
            lv[neg(b)].push_back(a);
        }
        else if (t==1)
        {
            lv[neg(a)].push_back(neg(b));
            lv[b].push_back(a);
        }
        else if (t==2)
        {
            lv[a].push_back(b);
            lv[neg(b)].push_back(neg(a));
        }
        else if (t==3)
        {
            lv[a].push_back(neg(b));
            lv[b].push_back(neg(a));
        }        
    }    
}

void sorttop(int nod)
{
    int i;
    v[nod]=1;
    for (i=0;i<lv[nod].size();i++)
        if (v[lv[nod][i]]==0)
            sorttop(lv[nod][i]);
    noduri.push_back(nod);
}

void dfs(int nod)
{
    int i;
    f[nod]=ct;
    for (i=0;i<lv2[nod].size();i++)
        if (f[lv2[nod][i]]==0)
            dfs(lv2[nod][i]);
}

int main()
{
    freopen("party.in","r",stdin);
    freopen("party.out","w",stdout);
    citire();
    v.resize(2*n+1);
    for (i=1;i<=2*n;i++)
        if (v[i]==0)
            sorttop(i);
    reverse(noduri.begin(), noduri.end());
    lv2.resize(2*n+1);
    for (i=1;i<=2*n;i++)
        for (j=0;j<lv[i].size();j++)
            lv2[lv[i][j]].push_back(i);    
    f.resize(2*n+1);    
    for (i=0;i<noduri.size();i++)
        if (f[noduri[i]]==0)
        {
            ct++;
            dfs(noduri[i]);            
        }
    ct=0;
    for (i=1;i<=n;i++)
        if (f[i]>f[i+n])
            ct++;
    printf("%d\n",ct);
    for (i=1;i<=n;i++)
        if (f[i]>f[i+n])
            printf("%d\n",i);
    return 0;
}