#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#define Dim 1001

struct vector
{
	int op,x,y;
}v[Dim];

char use[Dim];

int main()
{
	int N,M,nr,i,ok;

	freopen("party.in","r",stdin);

	scanf("%d%d",&N,&M);
 	for(i=1;i<=M;i++) scanf("%d%d%d",&v[i].x,&v[i].y,&v[i].op);

	srand(time(NULL));

	freopen("party.out","w",stdout);

	while(1)
	{
		nr=0;
		for(i=1;i<=N;i++)
		{
			use[i]=rand()%2;
			nr+=use[i];
		}

		ok=1;
		for(i=1;i<=M;i++)
			if(v[i].op==0)
			{
				if(use[v[i].x]|use[v[i].y]==0)
				{
					ok=0;
					break;
				}
			}
			else
			if(v[i].op==1)
			{
				if(use[v[i].x]==0&&use[v[i].y]!=0)
				{
					ok=0;
					break;
				}
			}
			else
			if(v[i].op==2)
			{
				if(use[v[i].y]==0&&use[v[i].x]!=0)
				{
					ok=0;
					break;
				}
			}
			else
			if(v[i].op==3)
			{
				if(use[v[i].x]&use[v[i].y]==1)
				{
					ok=0;
					break;
				}
			}

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

	return 0;
}