#include <bits/stdc++.h>
using namespace std;

ifstream fin("party.in");
ofstream fout("party.out");
const int NMAX = 102;
int n; int m;
vector<int> g[NMAX * 2];
vector<int> gt[NMAX * 2];
int ord[NMAX * 2]; int viz[NMAX * 2];
int solved[NMAX * 2];
bool existSolution = true;
int cnt;
int neg(int x) {
 if(x + n == 2 * n)
  return 2 * n;
 return (x + n) % (2 * n);
}
void read() {
 fin >> n >> m;
 for(int i = 1; i <= m ; ++i) {
  int x; int y; int z;
  fin >> x >> y >> z;

  if(z == 1)
   y = neg(y);
  if(z == 2)
   x = neg(x);
  if(z == 3)
   x = neg(x), y = neg(y);
  g[neg(x)].push_back(y);
  g[neg(y)].push_back(x);
  gt[y].push_back(neg(x));
  gt[x].push_back(neg(y));
 }

}
void dfs(int node) {
 viz[node] = 1;
 for(int x : g[node])
  if(viz[x] == 0)
   dfs(x);
 ord[++ord[0]] = node;
}
void dfsT(int node) {
 if(solved[node] == 1)
  existSolution = false;
 viz[node] = 1;
 solved[node] = 0;
 solved[neg(node)] = 1;
 for(int x : gt[node])
  if(viz[x] == 0)
   dfsT(x);
}
void solve() {

 for(int i = 1; i <= 2 * n; ++i)
  if(viz[i] == 0)
   dfs(i);
 memset(viz, 0, sizeof(viz));


 for(int i = ord[0]; i ; --i)
  if(viz[ord[i]] == 0 && viz[ neg(ord[i]) ] == 0)
   dfsT(ord[i]);

 for(int i = 1; i <= n ; ++i)
  if(solved[i] == 1)
   cnt++;
 fout << cnt << '\n';
 for(int i = 1; i <= n; ++i)
  if(solved[i] == 1)
   fout << i << '\n';
}
int main() {
 read();
 solve();
 return 0;
}