#include<cstdio>
#include<vector>

using namespace std;

const int NMAX = 100+5;
const int MMAX = 1000+5;

void Read(),Solve(),Print();

int N,M,Top,NrCTC;
vector<int> V[2*NMAX];    // graful implicatiilor
#define V (V+NMAX)
vector<int> W[2*NMAX];    // graful transpus al implicatiilor
#define W (W+NMAX)
bool Viz[2*NMAX];
#define Viz (Viz+NMAX)
int TSort[2*NMAX];
int Comp[2*NMAX];        // Comp[i] spune in ce componenta tare-conexa se afla nodul i
#define Comp (Comp+NMAX)
int Opus[2*NMAX];        // Opus[i] spune care este componenta tare-conexa simetrica lui i
int Sol[NMAX];
vector<int> CTC[2*NMAX]; // CTC[i] contine nodurile din a i-a componenta tare-conexa
vector<int> G[2*NMAX];   // graful rezultat dupa contractarea componentelor tare-conexe

void SortareTopologica(int nod)
{
    /* Sortare topologica a grafului initial */

    vector<int>::iterator it;
    Viz[nod]=1;
    for(it=V[nod].begin(); it!=V[nod].end(); it++)
    {
        if(Viz[*it]) continue;
        SortareTopologica(*it);
    }
    TSort[Top--]=nod;
}

void DFS(int nod)
{
    /* DFS pe graful transpus al grafului initial */

    vector<int>::iterator it;
    Viz[nod]=0;
    for(it=W[nod].begin(); it!=W[nod].end(); it++)
    {
        if(!Viz[*it]) continue;
        DFS(*it);
    }
    CTC[Top].push_back(nod);
    Comp[nod]=Top;
}

void ComponenteTareConexe()
{
    int i,x;

    Top=2*N;

    for(i=-N; i<=N; i++)
    {
        if(!i) continue;
        if(Viz[i]) continue;
        SortareTopologica(i);
    }

    for(i=1; i<=2*N; i++)
    {
        x=TSort[i];
        if(!Viz[x]) continue;
        Top++;
        DFS(x);
    }

    NrCTC=Top;
}

void ConstruiesteGraf()
{
    /* Fiecare componenta tare-conexa se contracta
       intr-un singur nod.                         */

    int i,x;
    vector<int>::iterator it,jt;

    for(i=1; i<=NrCTC; i++)
    {
        for(it=CTC[i].begin(); it!=CTC[i].end(); it++)
        {
            x=*it;
            for(jt=V[x].begin(); jt!=V[x].end(); jt++)
            {
                if(Comp[*jt]==i) continue;
                G[i].push_back(Comp[*jt]);
            }
        }
    }

    for(i=1; i<=N; i++)
    {
        Opus[Comp[i]]=Comp[-i];
        Opus[Comp[-i]]=Comp[i];
    }
}

void SorteazaTopologic(int nod)
{
    /* Sortare topologica a grafului contractat */

    vector<int>::iterator it;
    Viz[nod]=1;
    for(it=G[nod].begin(); it!=G[nod].end(); it++)
    {
        if(Viz[*it]) continue;
        SorteazaTopologic(*it);
    }
    TSort[Top--]=nod;
}

int main()
{
    Read();
    Solve();
    Print();

    return 0;
}

void Read()
{
    int x,y,z;

    freopen("party.in","r",stdin);
    freopen("party.out","w",stdout);

    scanf("%d%d",&N,&M);

    for(; M; --M)
    {
        scanf("%d%d%d",&x,&y,&z);

        if(z==1) y=-y;
        else if(z==2) x=-x;
        else if(z==3) x=-x,y=-y;

        /* Construirea grafului de implicatii
           x v y   <=>  (~x -> y) ^ (~y -> x) */

        V[-x].push_back(y);
        V[-y].push_back(x);
        W[y].push_back(-x);
        W[x].push_back(-y);
    }
}

void Solve()
{
    int i;
    vector<int>::iterator it;

    ComponenteTareConexe();

    ConstruiesteGraf();

    Top=NrCTC;

    for(i=1; i<=NrCTC; i++)
    {
        if(Viz[i]) continue;
        SorteazaTopologic(i);
    }

    for(i=1; i<=NrCTC; i++)
    {
        if(!Viz[i]) continue;
        for(it=CTC[i].begin(); it!=CTC[i].end(); it++)
            if(*it < 0) Sol[-(*it)]=1;
        Viz[i]=0;
        Viz[Opus[i]]=0;
    }
}

void Print()
{
    int i,ans=0;
    for(i=1; i<=N; i++)
        ans+=Sol[i];
    printf("%d\n",ans);
    for(i=1; i<=N; i++)
        if(Sol[i]) printf("%d\n",i);
}