#include<cstdio>
#include<vector>

using namespace std;

int M, n_ans, ans[109];

class SAT
{
    public:

    int n_Q, n_componente, N, sol[209], ap[209], Q[209];
    vector < int > v[209], h[209];

    int cod (int v)
    {
        if (v < 0) return N - v;
        return v;
    }

    int opus (int x)
    {
        if (x<=N) return N + x;
        return x - N;
    }

    void Add_Implication (int x, int y)
    {
        v [ cod ( x ) ] . push_back ( cod ( y ) );////graf normal
        h [ cod ( y ) ] . push_back ( cod ( x ) );////graf transpus
    }

    void Add_Clauza (int x, int y)
    {
        Add_Implication (-x, y);
        Add_Implication (-y, x);
    }

    void dfs (int nod)
    {
        ap[nod] = 1;
        for (vector < int > :: iterator it = v[nod].begin(); it != v[nod].end(); it++)
            if (ap[*it] == 0)
                dfs (*it);
        Q[++n_Q] = nod;
    }

    void dfp (int nod)
    {
        if (sol[nod])
        {
            sol[0] = -1;
            return ;
        }

        ap[nod] = 0;
        sol[opus(nod)] = 1;
        for (vector < int > :: iterator it = h[nod].begin(); it != h[nod].end(); it++)
            if (ap[*it] == 1)
                dfp (*it);
    }

    int solve ()
    {
        for (int i=1; i<=2*N; i++)
            if (ap[i] == 0)
                dfs (i);

        for (int i=n_Q; i>=1; i--)
            if (ap[Q[i]] && ap[opus(Q[i])])
                dfp (Q[i]);

        return sol[0];
    }
}sistem;

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

scanf ("%d %d", &sistem.N, &M);
for (int i=1; i<=M; i++)
{
    int X, Y, tip;
    scanf ("%d %d %d", &X, &Y, &tip);
    if (tip == 0) sistem . Add_Clauza (X, Y);
    else
    if (tip == 1) sistem . Add_Clauza (-Y, X);
    else
    if (tip == 2) sistem . Add_Clauza (-X, Y);
    else sistem . Add_Clauza (-X, -Y);
}

sistem.solve();

for (int i=1; i<=sistem.N; i++)
    if (sistem.sol[i])
        ans[++n_ans] = i;

printf ("%d\n", n_ans);
for (int i=1; i<=n_ans; i++)
    printf ("%d\n", ans[i]);

return 0;
}