#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

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

const int NMAX = 100;

struct Data {
  int x;
  int y;
  int z;
};

int n, m;
int p[1 + NMAX];
vector < int > sol;
Data v[1 + NMAX];

int main()
{
  in >> n >> m;
  fill(p + 1, p + n + 1, 1);

  for(int i = 1; i <= m; i++)
    in >> v[i].x >> v[i].y >> v[i].z;
  bool ok = false;

  while(ok == false) {
    ok = true;
    for(int i = 1; i <= m; i++) {
      Data &e = v[i];
      if(e.z == 0) {
        if(p[e.x] == 0 && p[e.y] == 0) {
          p[e.x] = p[e.y] = 1;
          ok = false;
          break;
        }
      }

      if(e.z == 1) {
        if(p[e.x] == 0 && p[e.y] != 0) {
          p[e.y] = 0;
          ok = false;
          break;
        }
      }

      if(e.z == 2) {
        if(p[e.y] == 0 && p[e.x] != 0) {
          p[e.x] = 0;
          ok = false;
          break;
        }
      }

      if(e.z == 3) {
        if(p[e.x] == 1 && p[e.y] == 1) {
          p[e.y] = 0;
          ok = false;
          break;
        }
      }
    }
  }

  for(int i = 1; i <= n; i++) {
    if(p[i] == 1)
      sol.push_back(i);
  }

  out << sol.size() << '\n';
  for(int i = 0; i < sol.size(); i++) {
    out << sol[i] << '\n';
  }

  in.close();
  out.close();
  return 0;
}