#include <cstdio>
#include <cstring>
#include <vector>
#include <stack>

using namespace std;

const int N = 202;

vector <int> graph [N], graph2 [N];
stack <int> st;
bool used [N];
int n, value [N];

inline int no (const int &x) {
    if (x > n)
        return x - n;
    else return n + x;
}

void dfs (int x) {
    vector <int> :: iterator it;

    used [x] = 1;
    for (it = graph [x].begin (); it != graph [x].end (); ++ it)
        if (!used [*it])
            dfs (*it);
    st.push (x);
}

void dfs2 (int x) {
    vector <int> :: iterator it;

    used [x] = 1;
    value [no (x)] = 1;
    for (it = graph2 [x].begin (); it != graph2 [x].end (); ++ it)
        if (!used [*it])
            dfs2 (*it);
}

int main () {
    int i,  a, b, m, ineg, c;
    vector <int> :: iterator it;

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

    scanf ("%d%d", &n, &m);
    for (i = 1; i <= m; i ++) {
        scanf ("%d%d%d", &a, &b, &c);
        if (c == 1)
            b = no (b);
        if (c == 2)
            a = no (a);
        if (c == 3) {
            a = no (a);
            b = no (b);
        }
        graph [no (a)].push_back (b);
        graph2 [b].push_back (no (a));
        graph [no (b)].push_back (a);
        graph2 [a].push_back (no (b));
    }
    for (i = 1; i <= 2 * n; i ++)
        if (!used [i])
            dfs (i);
    memset (used, 0, sizeof (used));
    while (!st.empty () ) {
        i = st.top ();
        ineg = no (i);
        st.pop ();
        if (!used [i] && !used [ineg]) {
            dfs2 (i);
        }
    }
    int ans = 0;
    for  (i = 1; i <= n; i ++)
        ans += value [i];
    printf ("%d\n", ans);
    for (i = 1; i <= n; i ++)
        if (value [i])
            printf ("%d\n", i);
    printf ("\n");
    return 0;
}