#include<fstream>
#include<stdio.h>
#include<iostream>
#include<stdlib.h>
#include<vector>
#include<string>
#include<math.h>
#include<ctime>

std::ifstream in("party.in");
std::ofstream out("party.out");

int N, M;

struct data
{
	int x;
	int y;
	int type;
};

int v[2000];

struct data d[2000];

int check(int i)
{
	if(d[i].type==0)
		return v[d[i].x] || v[d[i].y];
	else if(d[i].type == 1)
		return v[d[i].x] || ! v[d[i].y];
	else if(d[i].type == 2)
		return v[d[i].y] || ! v[d[i].x];
	else
		return !v[d[i].x] || !v[d[i].y];
	
	//v[d[i].x] + v[d[i].y] != 2;

}

void randomly(int i)
{
	if(rand()%2 == 0)
		v[d[i].x] = !v[d[i].x];
	else
		v[d[i].y] = !v[d[i].y];
}

void read()
{
	
	in>>N>>M;

	for(int j=1;j<=M;j++)
		in>>d[j].x>>d[j].y>>d[j].type;

	for(int j=1;j<=N;j++)
		v[j] = 1;
}

void calculate()
{
	int i;
	while(true)
	{
		for(i=1;i<=M;i++)
			if(check(i)==0)
			{
				randomly(i);
				break;
			}

		if(i==M+1)
			break;
	}
}

void print()
{
	int NR = 0;
	for(int i=1;i<=N;i++)
		if(v[i] == 1)
			NR++;
	
	out<<NR<<"\n";

	for(int i=1;i<=N;i++)
		if(v[i] == 1)
			out<<i<<"\n";
}

int main()
{
	read();
	
	calculate();

	print();



}