#include <fstream>
#include <vector>

#include <cstring>
using namespace std;

const int MAX_N = 102;

int N, M, ans;
int c[2 * MAX_N], sol[2 * MAX_N];
vector < int > v[2 * MAX_N], w[2 * MAX_N], scc[2 * MAX_N], a;
bool m[2 * MAX_N], s[2 * MAX_N];

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

void DFS1(int x) {
    m[x] = 1;
    for(size_t i = 0; i < v[x].size(); ++i)
        if(m[v[x][i]] == 0)
            DFS1(v[x][i]);
    a.push_back(x);
}

void DFS2(int x, int nr) {
    m[x] = 1;
    c[x] = nr;
    scc[nr].push_back(x);
    for(size_t i = 0; i < w[x].size(); ++i)
        if(m[w[x][i]] == 0)
            DFS2(w[x][i], nr);
}

int main() {
    ifstream f("party.in");
    ofstream g("party.out");

    f >> N >> M;
    for(int i = 1, x, y, t; i <= M; ++i) {
        f >> x >> y >> t;

        if(t == 1)
            y = neg(y);
        else if(t == 2)
            x = neg(x);
        else if(t == 3)
            x = neg(x), y = neg(y);

        v[neg(x)].push_back(y);
        v[neg(y)].push_back(x);

        w[y].push_back(neg(x));
        w[x].push_back(neg(y));
    }

    for(int i = 1; i <= 2 * N; ++i)
        if(m[i] == 0)
            DFS1(i);

    memset(m, 0, sizeof(m));
    int nr = 0;
    for(int i = a.size() - 1; i >= 0; --i)
        if(m[a[i]] == 0)
            DFS2(a[i], ++nr);

    for(int i = nr; i >= 1; --i) {
        if(s[i])
            continue;

        for(size_t j = 0; j < scc[i].size(); ++j) {
            int x = scc[i][j];

            sol[x] = 1;
            sol[c[neg(x)]] = 1;
        }
    }

    for(int i = 1; i <= N; ++i)
        ans += sol[i];

    g << ans << "\n";
    for(int i = 1; i <= N; ++i)
        if(sol[i])
            g << i << "\n";

    f.close();
    g.close();

    return 0;
}