#include <bits/stdc++.h>
#include <cstdlib>

using namespace std;

ifstream fin("party.in");
ofstream fout("party.out");

const int NMax = 1005;

int A[NMax];
int B[NMax];
int C[NMax];
int ans[NMax];

inline bool check(const int &x) {

    if(C[x] == 0) return ans[A[x]] || ans[B[x]];
    if(C[x] == 1 || C[x] == 2) return ans[A[x]] || !ans[B[x]];
    if(C[x] == 3) return !ans[A[x]] || !ans[B[x]];
}

int main() {

    ios::sync_with_stdio();
    fin.tie(NULL);

    int n, m;
    fin >> n >> m;

    for(int i = 1; i <= m; i++) fin >> A[i] >> B[i] >> C[i];

    for(int i = 1; i <= n; i++) ans[i] = true;

    for(int i = 1; i <= m; i++) {

        if(check(i) == false) {
            int ran = rand() % 2;
            if(ran == 1) {
                ans[B[i]] = !ans[B[i]];
            } else {
                ans[A[i]] = !ans[A[i]];
            }

            i = 0;
        }
    }

    int no = 0;
    for(int i = 1; i <= n; i++) {
        if(ans[i] == true) no++;
    }

    fout << no << "\n";

    for(int i = 1; i <= n; i++) {
        if(ans[i] == true) fout << i << "\n";
    }

    return 0;
}