/* 
 * File:   party-probabilistic.cpp
 * Author: Vlad Paunescu
 *
 * Created on January 30, 2014, 12:32 AM
 * 
 * randomized algorithm for 2-SAT problem
 */

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



using namespace std;

typedef struct _clause {
    int x, y, type;
} Clause;

const int MAX_N = 102;
const int MAX_M = 1002;

int n, m;

Clause clause[MAX_M];
bool assign[MAX_N];

void solve() {
    bool done = false;
    int r;

    while (!done) {
        done = true;
        for (int i = 1; i <= m; ++i) {
            if (clause[i].type == 0) {
                // x or y must attend the party
                if (!assign[clause[i].x] && !assign[clause[i].y]) {
                    r = rand() % 2;
                    if (r) assign[clause[i].x] = true;
                    else assign[clause[i].y] = true;
                    done = false;
                }
            } else if (clause[i].type == 1) {
                // if x attends there is no restriction for y
                // but if x does not attend, then y must not attend too
                if (!assign[clause[i].x] && assign[clause[i].y]) {
                    assign[clause[i].y] = false;
                    done = false;
                }
            } else if (clause[i].type == 2) {
                // if y attends there is no restriction for x
                // but if y does not attend, then x must not attend too
                if (assign[clause[i].x] && !assign[clause[i].y]) {
                    assign[clause[i].x] = false;
                    done = false;
                }
            } else if (clause[i].type == 2) {
                // at least one of x and y does not attend the party
                if (assign[clause[i].x] && assign[clause[i].y]) {
                    rand() % 2 ? assign[clause[i].x] = false
                            : assign[clause[i].y] = false;
                    done = false;
                }
            }
        }
    }
}

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

    srand(time(NULL));


    scanf("%d %d", &n, &m);
    for (int i = 1; i <= m; i++) {
        scanf("%d %d %d", &clause[i].x, &clause[i].y, &clause[i].type);
    }


    int vars = 0;
    while (vars == 0) {
        vars = 0;
        for (int i = 1; i <= n; ++i) assign[i] = rand() % 2;
        solve();

        for (int i = 1; i <= n; ++i) {
            if (assign[i]) {
                vars++;
            }
        }
    }

    printf("%d\n", vars);
    for (int i = 1; i <= n; ++i) {
        if (assign[i]) {
            printf("%d\n", i);
        }
    }
    return 0;
}