#include <cstdio>
#include <cstdlib>
#include <vector>
#include <algorithm>
using namespace std;

const int NMAX = 210;

int N, M, X, Y, Z, TopSort[NMAX], Val[NMAX];
bool Used[NMAX];
vector<int> G[NMAX], GT[NMAX];

int Neg(int X)
{
    if(X <= N) return X + N;
    else return X - N;
}

void DFP(int Node)
{
    Used[Node] = 1;
    for(vector<int> :: iterator it = G[Node].begin(); it != G[Node].end(); ++ it)
        if(!Used[*it])
            DFP(*it);
    TopSort[ ++ TopSort[0] ] = Node;
}

void DFM(int Node)
{
    Val[ Neg(Node) ] = 1;
    Used[Node] = 0;

    for(vector<int> :: iterator it = GT[Node].begin(); it != GT[Node].end(); ++ it)
        if(Used[*it])
            DFM(*it);
}

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

    scanf("%i %i", &N, &M);
    for(int i = 1; i <= M; ++ i)
    {
        scanf("%i %i %i", &X, &Y, &Z);

        if(Z == 1) Y = Neg(Y);
        else if(Z == 2) X = Neg(X);
        else if(Z == 3) X = Neg(X), Y = Neg(Y);

        G[Neg(Y)].push_back(X);
        GT[X].push_back(Neg(Y));
        G[Neg(X)].push_back(Y);
        GT[Y].push_back(Neg(X));
    }

    for(int i = 1; i <= 2 * N; ++ i)
        if(!Used[i])
            DFP(i);
    reverse(TopSort + 1, TopSort + TopSort[0] + 1);
    for(int i = 1; i <= 2 * N; ++ i)
        if(Used[ TopSort[i] ] && Used[ Neg(TopSort[i]) ])
            DFM(TopSort[i]);

    int Ans = 0;
    for(int i = 1; i <= N; ++ i) Ans += Val[i];

    printf("%i\n", Ans);
    for(int i = 1; i <= N; ++ i)
        if(Val[i])
            printf("%i\n", i);
}