#include <bits/stdc++.h>
#define maxN 102
using namespace std;
int n, m, vis[maxN], f[maxN], inv[maxN], ans;
vector < int > V[maxN], v[maxN];
int Not(int x)
{
    if (x <= n)
        return x + n;
    return x - n;
}
void dfs(int x)
{
    vis[x] = 1;
    int i, l = V[x].size();
    for (i = 0; i < l; ++ i)
        if (!vis[V[x][i]])
            dfs(V[x][i]);

    f[++ f[0]] = x;
}
void DFS(int x)
{
    vis[x] = 0;
    if (!inv[Not(x)] && x > n)
        ++ ans;
    inv[Not(x)] = 1;
    int i, l = v[x].size();
    for (i = 0; i < l; ++ i)
        if (vis[v[x][i]])
            DFS(v[x][i]);
}
void add_edge(int x, int y)
{
    //// x | y
    V[Not(x)].push_back(y);
    v[y].push_back(Not(x));
    V[Not(y)].push_back(x);
    v[x].push_back(Not(y));
}
void read()
{
    freopen("party.in", "r", stdin);
    scanf("%d %d", &n, &m);
    while (m --)
    {
        int x, y, op;
        scanf("%d %d %d", &x, &y, &op);
        if (!op)
            add_edge(x, y);
        else if (op == 1)
            add_edge(x, Not(y));
        else if (op == 2)
            add_edge(Not(x), y);
        else
            add_edge(Not(x), Not(y));
    }
}
void solve()
{
    int i;
    for (i = 1; i <= 2 * n; ++ i)
        if (!vis[i])
            dfs(i);
    for (i = f[0]; i >= 1; -- i)
        if (vis[f[i]] && vis[Not(f[i])])
            DFS(f[i]);
}
void write()
{
    int i;
    freopen("party.out", "w", stdout);
    printf("%d\n", ans);
    for (i = 1; i <= n; ++ i)
        if (inv[i])
            printf("%d\n", i);
}
int main()
{
    read();
    solve();
    write();
    return 0;
}