#include <stdio.h>
#define NMAX 1024
#define MMAX 128

struct cerinta { int x, y, z; } A[NMAX];

int P[MMAX];
int N, M, ok, i, X, Y, Z, Cnt;


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

     scanf("%d %d", &N, &M);

     for (i = 1; i <= N; i++) P[i] = 0;

     for (i = 1; i <= M; i++) scanf("%d %d %d", &A[i].x, &A[i].y, &A[i].z);

     ok = 0;

     while (ok == 0)
     {
          ok = 1;

          for (i = 1; i <= M; i++)
          {
              X = A[i].x, Y = A[i].y, Z = A[i].z;

              if (Z == 0)
                    if (P[X] == 0 && P[Y] == 0) { P[Y] = 1; ok = 0; break;}

              if (Z == 1)
                    if (P[X] == 0 && P[Y] != 0) { P[Y] = 0; ok = 0; break; }

              if (Z == 2)
                    if (P[Y] == 0 && P[X] != 0) { P[X] = 0; ok = 0; break; }

              if (Z == 3)
                    if (P[X] == 1 && P[Y] == 1) { P[X] = 0; ok = 0; }

          }
     }

     for (i = 1; i <= N; i++)
            if (P[i]) Cnt++;

     printf("%d\n", Cnt);

     for (i = 1; i <= N; i++)
            if (P[i]) printf("%d\n", i);


     return 0;
}