#include <cstdio>
#define NMax 1000

int pos[5][NMax+1][NMax+1];
int atins[NMax+1];
int is[NMax+1];
int x[NMax+1];
int y[NMax+1];
int z[NMax+1];
int N,M,nr,deja=1;

void Write()
{
    int i;
    for(i = 1; i <= N; ++i)
    if( is[i] ) ++nr;

    if(nr)
    {
        printf("%d\n",nr);
        for(i = 1; i <= N; ++i)
        if( is[i] ) printf("%d\n",i);
        deja = 0;
    }
}

void Gen(int k)
{
    if(k==N+1)
        if(deja) Write();
        else;
    else{
        int i,j,ok=1;

        if( is[k] != -1 ) Gen(k+1);
        else{

            is[k] = 0;
            for(j = 1; j <= pos[0][k][0] && deja; ++j)
            if( is[ pos[0][k][j] ] < 0 )
            {
                is[ pos[0][k][j] ] = 1;
                atins[ pos[0][k][j] ] = k;
            }
            else if( is[ pos[0][k][j] ] != 1 ) { ok = 0; break; }

            for(j = 1; j <= pos[1][k][0] && deja; ++j)
            if( is[ pos[1][k][j] ] < 0 )
            {
                is[ pos[1][k][j] ] = 0;
                atins[ pos[1][k][j] ] = k;
            }
            else if( is[ pos[1][k][j] ] != 0 ) { ok = 0; break; }

            if(ok && deja) Gen(k+1);
            for(i = k+1; i <= N; ++i)
            if( atins[i] == k ) { atins[i] = 0; is[i] = -1; }

            ok = is[k] = 1;
            for(j = 1; j <= pos[2][k][0] && deja; ++j)
            if( is[ pos[2][k][j] ] < 0 )
            {
                is[ pos[2][k][j] ] = 1;
                atins[ pos[2][k][j] ] = k;
            }
            else if( is[ pos[2][k][j] ] != 1 ) { ok = 0; break; }

            for(j = 1; j <= pos[3][k][0] && deja; ++j)
            if( is[ pos[3][k][j] ] < 0 )
            {
                is[ pos[3][k][j] ] = 0;
                atins[ pos[3][k][j] ] = k;
            }
            else if( is[ pos[3][k][j] ] != 0 ) { ok = 0; break; }

            if(ok && deja) Gen(k+1);
            for(i = k+1; i <= N; ++i)
            if( atins[i] == k ) { atins[i] = 0; is[i] = -1; }

            is[k] = -1;
        }
    }
}

void Compute()
{
    int i,j;

    for(i = 1; i <= N; ++i)
    {
        for(j = 1; j <= M; ++j)
        if( x[j] == i && z[j] == 0 ) pos[0][i][ ++pos[0][i][0] ] = y[j];
        else if( y[j] == i && z[j] == 0 ) pos[0][i][ ++pos[0][i][0] ] = x[j];
        else if( x[j] == i && z[j] == 1 ) pos[1][i][ ++pos[1][i][0] ] = y[j];
        else if( y[j] == i && z[j] == 1 ) pos[2][i][ ++pos[2][i][0] ] = x[j];
        else if( y[j] == i && z[j] == 2 ) pos[1][i][ ++pos[1][i][0] ] = x[j];
        else if( x[j] == i && z[j] == 2 ) pos[2][i][ ++pos[2][i][0] ] = y[j];
        else if( x[j] == i && z[j] == 3 ) pos[3][i][ ++pos[3][i][0] ] = y[j];
        else if( y[j] == i && z[j] == 3 ) pos[3][i][ ++pos[3][i][0] ] = x[j];
    }
}

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

    int i;

    scanf("%d %d",&N,&M);
    for(i = 1; i <= M; ++i) scanf("%d %d %d",&x[i], &y[i], &z[i]);
    for(i = 1; i <= N; ++i) is[i] = -1;
    Compute();
    Gen(1);



return 0;
}