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



using namespace std;

int n, m;
int pr[3][1024];
int cond[1024], val[1024];

inline int probeaza(int ind)
{
 if (cond[ind] == 0)
  return (val[pr[0][ind]] | val[pr[1][ind]]);
 if (cond[ind] == 3)
  return ((!val[pr[0][ind]]) | (!val[pr[1][ind]]));
 return (val[pr[0][ind]] | (!val[pr[1][ind]]));
}

int main()
{
 srand(time(0));
 freopen("party.in", "r", stdin);
 freopen("party.out", "w", stdout);

 scanf("%d %d", &n, &m);

 for (int i = 1; i <= m; i++)
 {
  scanf("%d %d %d", &pr[0][i], &pr[1][i], &cond[i]);

  if (cond[i] == 2)
  {
   swap(pr[0][i], pr[1][i]);
   cond[i] = 1;
  }
 }

 for (int i = 1; i <= n; i++)
  val[i] = 1;

 for (int ok = 0; !ok; )
 {
  ok = 1;
  for (int i = 1; i <= m; i++)
   if (!probeaza(i))
   {
    ok = 0;

    int sch = rand() % 2;
    val[pr[sch][i]] ^= 1;
   }
 }

 int nr = 0;
 for (int i = 1; i <= n; i++)
  nr += val[i];

 printf("%d\n", nr);
 for (int i = 1; i <= n; i++)
  if (val[i])
   printf("%d\n", i);

 fclose(stdin);
 fclose(stdout);
 return 0;
}