#include <stdio.h>#include <cstring>
#include <vector>
using namespace std;


vector <int> G[210], Gt[210], V[210];
int C[210], R[210], out[210];
int viz[210], st[210];
int n, m, k;
int pun = 1, comp, pas;
inline int real(int x){
 if(x > 0) return x;
 return n-x;
}
inline void go_muchii(int x, int y){
 G[real(-x)].push_back(real(y));
 G[real(-y)].push_back(real(x));

 Gt[real(y)].push_back(real(-x));
 Gt[real(x)].push_back(real(-y));
}
void df(int x, vector<int> G[]){
 viz[x] = 1;
 if(!pas) C[x] = comp;
 for(vector<int>::iterator i = G[x].begin(); i != G[x].end(); ++i)
  if(!viz[*i])
   df(*i, G);
 out[x] = ++k;
 if(pun) st[++st[0]] = x;
}
void CTC(){
 for(int i = 1; i <= 2*n; ++i)
  if(!viz[i])
   df(i, G);
 pun = 0;
 memset(viz, 0, (2*n+3)*sizeof(viz[0]));
 for(int i = st[0]; i; --i)
  if(!viz[st[i]]){
   comp++;
   df(st[i], Gt);
  }

 for(int x = 1; x <= 2*n; ++x)
  for(vector<int>::iterator i = G[x].begin(); i != G[x].end(); ++i)
   if(C[x] != C[*i]) V[C[x]].push_back(C[*i]);

 memset(viz, 0, (2*n+3)*sizeof(viz[0]));
 k = 0;
 pas = 1;
 for(int x = 1; x <= comp; ++x)
  if(!viz[x])
   df(x, V);
}
void sat() {
 for(int x = 1; x <= n; ++x)
  if( out[C[x]] < out[C[real(-x)]]) R[C[x]] = 1;
  else R[C[real(-x)]] = 1;
 int c = 0;
 for(int i = 1; i <= n; ++i)
  if(R[C[i]]) c++;
 printf("%d\n", c);
 for(int i = 1; i <= n; ++i)
  if(R[C[i]]) printf("%d\n", i);
}
int main(){
 freopen("party.in", "r", stdin);
 freopen("party.out", "w", stdout);
 scanf("%d%d", &n, &m);
 for(int i = 1; i <= m; ++i){
  int x, y, c;
  scanf("%d%d%d", &x, &y, &c);
  if(c==0) ;
  else if(c == 1) y = -y;
  else if(c==2) x = -x;
  else {x = -x; y = -y;}
  go_muchii(x, y);
 }
 CTC();
 sat();
 return 0;
}