#include<iostream>
#include<ctime>
#include<cstdio>
#include<cstdlib>

#define M_MAX 1010
#define N_MAX 1010
using namespace std;

typedef struct cerinta {
    int x;
    int y;
    int z;
} cer;
cer c[M_MAX];

int v[N_MAX];
int main()
{
    srand(time(NULL));
    int n, m, ok, r;

    FILE *fin, *fout;
    fin = fopen("party.in", "r");
    fout=fopen("party.out", "w");

    fscanf(fin, "%d %d", &n, &m);

    for(int i=0; i<m; i++)
    {
        fscanf(fin, "%d %d %d", &c[i].x, &c[i].y, &c[i].z);
    }
    for(int i=1; i<=n; i++)
        v[i]=1;
    ok=0;
    while( !ok ) {
        ok=1;
        for(int i=0; i<m; i++) {
            if(c[i].z == 0) {
                if(v[c[i].x] == 0 && v[c[i].y] == 0)
                {
                    r = rand() % 2;
                    if(r == 0)
                        v[c[i].x] = 1;
                    else
                        v[c[i].y] = 1;
                    ok = 0;
                }
            }
            if(c[i].z == 1) {
                if(v[c[i].x] == 0 && v[c[i].y] == 1)
                {
                    r = rand() % 2;
                    if(r == 0)
                        v[c[i].x] = 1;
                    else
                        v[c[i].y] = 0;
                    ok = 0;
                }
            }
            if(c[i].z == 2) {
                if(v[c[i].x] == 1 && v[c[i].y] == 0) {
                    r = rand() % 2;
                    if(r == 0)
                        v[c[i].x] = 0;
                    else
                        v[c[i].y] = 1;
                    ok = 0;
                }
            }
            if(c[i].z == 3)
            {
                if(v[c[i].x] == 1 && v[c[i].y] == 1) {
                    r = rand() % 2;
                    if(r == 0)
                        v[c[i].x] = 0;
                    else
                        v[c[i].y] = 0;
                    ok = 0;
                }
            }
        }
    }
    int nr=0;
    for(int i=1; i <= n; i++)
        if(v[i]==1)
            nr++;
    fprintf(fout, "%d\n", nr);
    for(int i=1; i<=n; i++)
        if(v[i])
            fprintf(fout, "%d\n", i);
}