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

#define DIM 1011

struct cer {
	int x;
	int y;
	int t;
};

int C[4][2][2] = {{{0,1},{1,1}},   {{1,0},{1,1}},   {{1,1},{0,1}},   {{1,1},{1,0}}};

cer v[DIM];

int u[DIM/10];

int n,m,ok,tot,i,aux,poz;

int main(){
	FILE *f = fopen("party.in","r");
	fscanf(f,"%d %d",&n, &m);
	for (i = 1;i<=m;i++){
		fscanf(f,"%d %d %d", &v[i].x, &v[i].y, &v[i].t);
	}
	fclose(f);
	
//	for (i=1;i<=n;i++)
//		u[i] = 1;
	
	do{
		ok = 1;
		for (i=1;i<=m;i++) {
			if (!C[v[i].t][u[v[i].x]][u[v[i].y]]) {
				ok = 0;
				if (aux = rand()%2) {
					u[v[i].x] = 1 - u[v[i].x];
				} else {
					u[v[i].y] = 1 - u[v[i].y];
				}
				break;
			}
		}
		tot = 1;
		if (ok) {
			tot = 0;
			for (i=1;i<=n;i++){
				if (u[i]){
					tot++;
				}
			}
			if (!tot){
				if (aux = rand()%2) {
					u[v[1].x] = 1;
				} else {
					u[v[1].y] = 1;
				}
				continue;
			}
		}
		
	} while (!ok || !tot);
	
	tot = 0;
	for (i=1;i<=n;i++)
		if (u[i])
			tot++;
	FILE *g = fopen("party.out","w");
	fprintf(g,"%d\n",tot);
	for (i=1;i<=n;i++)
		if (u[i])
			fprintf(g,"%d\n",i);
	fclose(g);
		
	
	return 0;
}