#include<stdio.h>
#include<iostream>
#include<string.h>
#include<vector>
using namespace std;

#define pb push_back
#define inv(a) (a<=n ? a+n : a-n)
#define NMAX 10004

vector<int> v[NMAX],vt[NMAX];
int t[NMAX],nrt,n,m,sol[NMAX];
int a=0,b=0,tip=-1;
char viz[NMAX];

void dfs(int nod)
{
	viz[nod]=1;	
	int i,vec,lim=v[nod].size();

	for(i=0;i<lim;i++)
		if(!viz[vec=v[nod][i]])
			dfs(vec);
	t[++nrt]=nod;
}

void dfs2(int nod)
{
	viz[nod]=1;
	sol[inv(nod)]=1;

	int i,vec,lim=vt[nod].size();
	
	for(i=0;i<lim;i++)	
		if(!viz[vec=vt[nod][i]])
			dfs2(vec);

}

int main ()
{
	int i;

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

	scanf("%d%d",&n,&m);
	
	for(i=1;i<=m;i++)
	{
		scanf("%d%d%d",&a,&b,&tip);
//		printf("%d %d %d\n",a,b,tip);
	
		if(!tip)
		{
			v[inv(a)].pb(b);
			v[inv(b)].pb(a);
			vt[b].pb(inv(a));
			vt[a].pb(inv(b));
		}
		else if(tip==1)
		{
			v[inv(a)].pb(inv(b));
			vt[inv(b)].pb(inv(a));
			v[b].pb(a);
			vt[a].pb(b);
			//printf("muchie %d %d\nmuchie %d %d\n",inv(a),inv(b),b,a);
		}
		else if(tip==2)
		{
			v[inv(b)].pb(inv(a));
			vt[inv(a)].pb(inv(b));
			v[a].pb(b);
			vt[b].pb(a);
		}
		else
		{
			vt[inv(a)].pb(b);
			vt[inv(b)].pb(a);
			v[b].pb(inv(a));
			v[a].pb(inv(b));
//			printf("muchie %d %d\nmuchie %d %d\n",b,inv(a),a,inv(b));
		}
		
	}
	
	for(i=1;i<=2*n;i++)
		if(!viz[i])
			dfs(i);
	memset(viz,0,sizeof(viz));

//	printf("/////%d\n",t[2*n]);
	for(i=2*n;i>=1;i--)
		if(!viz[t[i]] && !viz[inv(t[i])])
			dfs2(t[i]);

	for(i=1;i<=n;i++)
		if(sol[i])
			sol[0]++;

	printf("%d\n",sol[0]);

	for(i=1;i<=n;i++)
		if(sol[i])
			printf("%d\n",i);
	return 0;
}