#include <bits/stdc++.h>
#define rand() dis(gen)
using namespace std;

const int N = 1005;
mt19937 gen(time(0));
uniform_int_distribution<int> dis(0, 1e6);

int i, n, m, x[N], y[N], z[N], val[N], nx[N], ny[N], rs;

int main() {
  ifstream cin("party.in");
  ofstream cout("party.out");
  ios_base::sync_with_stdio(0);

  cin >> n >> m;
  for(i = 1; i <= m; ++i) {
    cin >> x[i] >> y[i] >> z[i];

    if(z[i] == 1) ny[y[i]] = 1;
    if(z[i] == 2) nx[x[i]] = 1;
    if(z[i] == 3) nx[x[i]] = ny[y[i]] = 1;
  }

  for(i = 1; i <= m; ++i)
    if(!(val[x[i]] ^ nx[x[i]]) && !(val[y[i]] ^ ny[y[i]])) {
      if(rand() & 1) val[x[i]] ^= 1;
      else val[y[i]] ^= 1;
      i = 0;
    }

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

  cout << rs << '\n';
  for(i = 1; i <= n; ++i) if(val[i]) cout << i << '\n';

  return 0;
}