#include <bits/stdc++.h>
#define DIM 210
using namespace std;

vector <int> L[DIM],ans;
int level[DIM],low[DIM],viz[DIM],sol[DIM];
deque <int> s;
int n,m,i,x,y,tip,idx,nx,ny;

void dfs (int nod){

    level[nod] = low[nod] = ++idx;
    viz[nod] = 1;
    s.push_back(nod);
    for (auto vecin : L[nod]){
        if (!level[vecin]){
            dfs (vecin);
            low[nod] = min (low[nod],low[vecin]);
        } else {
            if (viz[vecin])
                low[nod] = min (low[nod],low[vecin]);
        }
    }
    if (low[nod] == level[nod]){
        int x;
        do{
            x = s.back();
            int nx;
            if (x <= n)
                nx = x + n;
            else nx = x - n;

            if (sol[x] == 0){
                sol[x] = 1;
                sol[nx] = -1;
            }

            s.pop_back();
            viz[x] = 0;

        } while (x != nod);

    }
}

int main (){

    ifstream fin ("party.in");
    ofstream fout ("party.out");

    fin>>n>>m;
    for (i=1;i<=m;i++){
        fin>>x>>y>>tip;
        if (tip == 0){
             nx = x + n;
             ny = y + n;
        } else {
            if (tip == 1){
                nx = x + n;
                ny = y;
                y += n;
            } else {
                if (tip == 2){
                    nx = x;
                    x += n;
                    ny = y + n;
                } else {
                    nx = x;
                    x += n;
                    ny = y;
                    y += n;
                }}}

        L[nx].push_back(y);
        L[ny].push_back(x);
    }


    for (i=1;i<=2*n;i++){
        if (!viz[i])
            dfs (i);
    }

    for (i=1;i<=n;i++)
        if (sol[i] == 1)
            ans.push_back(i);

    sort (ans.begin(),ans.end());
    fout<<ans.size()<<"\n";
    for (auto it : ans)
        fout<<it<<"\n";


    return 0;
}