#include <fstream>

using namespace std;

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

const int nmax= 100;
const int mmax= 1000;

int n, m, sol;

bool u[nmax+1];
int x[mmax+1], y[mmax+1];

int main(  ) {
    fin>>n>>m;
    for ( int i= 1, k; i<=m; ++i ) {
        fin>>x[i]>>y[i]>>k;
        if ( k==1 || k==3 ) {
            x[i]= -x[i];
        }
        if ( k==2 || k==3 ) {
            y[i]= -y[i];
        }
    }
    for ( int i= 1; i<=n; ++i ) {
        u[i]= 1;
    }

    for ( int ok= 0; ok==0; ) {
        ok= 1;
        for ( int i= 1; i<=m && ok==1; ++i ) {
            if ( x[i]>0 && y[i]>0 && u[x[i]]==0 && u[y[i]]==0 ) {
                u[x[i]]= u[y[i]]= 1;
                ok= 0;
            } else if ( x[i]<0 && y[i]>0 && u[-x[i]]==0 && u[y[i]]==1 ) {
                u[y[i]]^= 1;
                ok= 0;
            } else if ( x[i]>0 && y[i]<0 && u[x[i]]==1 && u[-y[i]]==0 ) {
                u[x[i]]^= 1;
                ok= 0;
            } else if ( x[i]<0 && y[i]<0 && u[-x[i]]==1 && u[-y[i]]==1 ) {
                u[-y[i]]^= 1;
                ok= 0;
            }
        }
    }

    for ( int i= 1; i<=n; ++i ) {
        if ( u[i]==1 ) {
            ++sol;
        }
    }

    fout<<sol<<"\n";
    for ( int i= 1; i<=n; ++i ) {
        if ( u[i]==1 ) {
            fout<<i<<"\n";
        }
    }

    return 0;
}