Korn

input/code.cpp: In function 'int main()':
input/code.cpp:63:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     if (v[i].size() == p->first) ans.push_back(i);
                                           ^
input/code.cpp:71:64: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 1; i <= n; i++) if (v[i].size() == p->first) ei = i;
                                                                ^
input/code.cpp:76:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     if (v[i].size() == t && !e[i]) {
                                        ^

#include <bits/stdc++.h>

#define uint unsigned int
#define ull unsigned long long
#define INF 999999999
#define LINF 999999999999999999
#define ll long long
#define ld long double
#define M 1000000007
#define E 0.0000001
#define N (1<<18)
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pdd pair<double, double>
#define pld pair<long double, long double>
#define cll complex<long long>
#define cld complex<long double>
#define X real()
#define Y imag()
#define C 'a'
#define F first
#define S second
#define PI 3.1415926535897932384626433

using namespace std;

vector<int> v[500001];
bool e[500001];
int ei;

bool dfs (int i, bool f) {
    if (i == ei) return 1;
    if (e[i]) return 1;
    e[i] = true;
    if (v[i].size() > 2 && !f) return 0;
    for (int j : v[i]) if (!dfs(j, false)) return false;
    return true;
}

int main () {
    int n, m;
    cin>>n>>m;
    for (int i = 0; i < m; i++) {
        int a, b;
        cin>>a>>b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    map<int, int> w;
    for (int i = 1; i <= n; i++) {
        if (v[i].size() % 2) {
            cout<<0<<endl;
            return 0;
        }
        w[v[i].size()]++;
    }
    if (w.size() > 1) {
        auto p = --(w.end());
        if (w.size() == 2) {
            if (p->second < 3) {
                vector<int> ans;
                for (int i = 1; i <= n; i++) {
                    if (v[i].size() == p->first) ans.push_back(i);
                }
                cout<<ans.size()<<endl;
                for (int i : ans) cout<<i<<" ";
                cout<<endl;
            }
        } else if (p->second > 1) cout<<0<<endl;
        else {
            for (int i = 1; i <= n; i++) if (v[i].size() == p->first) ei = i;
            --p;
            while (true) {
                int t = p->first;
                for (int i = 1; i <= n; i++) {
                    if (v[i].size() == t && !e[i]) {
                        if (!dfs(i, true)) cout<<0<<endl, exit(0);
                    }
                }
                if (p == w.begin()) break;
                --p;
            }
            cout<<1<<endl<<ei<<endl;
        }
    } else if (w.size() == 1) {
        if (w.begin()->first == 2) {
            cout<<n<<endl;
            for (int i = 1; i <= n; i++) cout<<i<<" ";
            cout<<endl;
        } else cout<<0<<endl;
    }
}

/**
9 3
1 2 a
2 3 b
2 4 a
4 5 b
4 6 c
6 7 d
6 8 a
8 9 b
acb

9 12
1 2
1 3
1 4
1 5
1 6
1 7
2 8
3 8
4 9
5 9
6 9
7 9
*/

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: WRONG ANSWER

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED