#include <fstream>
#include <cstring>

using namespace std;

bool p[101];
bool done = false;

struct Cond
{
    int x, y;
    unsigned char c;

    void processCondition()
    {
        if (c == 0)
            if (!p[x] && !p[y])
            {
                p[x] = true;
                p[y] = true;
                done = false;
            }
        else if (c == 1)
            if (!p[x] && p[y])
            {
                p[y] = false;
                done = false;
            }
        else if (c == 2)
            if (!p[y] && p[x])
            {
                p[x] = false;
                done = false;
            }
        else if (c == 3)
            if (p[x] && p[y])
            {
                p[y] = false;
                done = false;
            }
    }
};

int main()
{
    memset(p, true, sizeof(int) * 101);
    ifstream input("party.in");
    int n, m, i;
    Cond cond[1000];

    input >> n >> m;

    for (i = 0; i < m; i++)
    {
        Cond &c = cond[i];
        input >> c.x >> c.y >> c.c;
    }

    while (!done)
    {
        done = true;
        for (i = 0; i < m; i++)
            cond[i].processCondition();
    }

    ofstream output("party.out");

    int count = 0;

    for (i = 1; i <= n; i++)
        count++;
    output << count << '\n';

    for (i = 1; i <= n; i++)
        if (p[i])
            output << i << '\n';

    return 0;
}