#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vector>
#include <stack>

using namespace std;

const int N = 210;

int noInvit , noCond , typeCond ;

vector < int > edges [ N ];

int varValues [ N ];

stack < int > stk ;
int inStack [ N ];

int low [ N ] , preord [ N ] , nrCr = 1 ,nrSol ;

void CalculateSCC( int node ){
    vector < int >::iterator it ;
    int vec ;

    stk.push( node );
    inStack [ node ] = 1 ;
    low [ node ] = preord [ node ] = nrCr ++ ;

    for ( it = edges [ node ].begin() ; it != edges [ node ].end() ; it++ ){
        vec = *it ;

        if ( !preord [ *it ] ){

            CalculateSCC( *it );
            low[ node ] = min( low [ node ] , low[ *it ] );

        }else{
            if ( inStack [ *it ] ){
                low [ node ] = min ( low [ node ] , low [ *it ] );
            }
        }
    }

    if ( low [ node ] == preord [ node ] ){
        int x ;
        do {
            x = stk.top() ;
            stk.pop() ;
            inStack [ x ] = 0 ;

            if ( x > noInvit ){
                if ( varValues [ x - noInvit ] == -1 ){
                    varValues [ x - noInvit ] = 0 ;
                }
            }else{
                if ( varValues [ x ] == -1 ){
                    varValues [ x ] = 1 ;
                    nrSol++;
                }
            }
//            printf("%d ",x );
        }while ( x != node );
//        printf("\n");
    }

}

int main(){
    int i , x , y , xnot , ynot ;

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

    scanf("%d%d",&noInvit , &noCond );

    for ( i = 0 ; i < noCond ; i++ ){
        scanf("%d%d%d", &x , &y , &typeCond );

        xnot = x + noInvit ;
        ynot = y + noInvit ;

        switch( typeCond ){
        case 0 :
            edges[ xnot ].push_back( y );
            edges[ ynot ].push_back( x );
            break ;
        case 1 :
            edges[ xnot ].push_back( ynot );
            edges[ y ].push_back( x );
            break ;
        case 2 :
            edges[ x ].push_back( y );
            edges[ ynot ].push_back( xnot );
            break ;
        case 3 :
            edges[ x ].push_back( ynot );
            edges[ y ].push_back( xnot );
            break ;
        }
    }

    memset ( varValues , -1 , sizeof varValues );

    for ( i = 1 ; i <= 2 * noInvit ; i ++ ){
        if ( preord [ i ] == 0 )
            CalculateSCC( i );
    }

    printf("%d\n",nrSol);
    for ( i = 1 ; i <= noInvit ; i++ ){
        if ( varValues [ i ] == 1 ){
            printf("%d\n",i);
        }
    }

    return 0;
}