#include "bits/stdc++.h"
#ifndef err
#define err(...)(void)0
#endif
using namespace std;
using ll = long long;
using ull = decltype(1ull);
template<class T>int size(T&&a) { return a.size(); }
#define REP(t,a)for(typename make_signed<decltype(a.second)>::type t=a.first,_l##t=a.second;t<_l##t;t++)
#define RREP(t,a)for(typename make_signed<decltype(a.second)>::type t=a.second-1,_l##t=a.first;t>=_l##t;t--)
template<class B>pair<int, B>make_pair(B b) { return{ 0,b }; }
#define rep(t,...)REP(t,make_pair(__VA_ARGS__))
#define rrep(t,...)RREP(t,make_pair(__VA_ARGS__))
#define all(a)begin(a),end(a)
#define rall(a)a.rbegin(),a.rend()
#define var(t, ...) t __VA_ARGS__;in,__VA_ARGS__;

void Calc();
int main() {
  ios::sync_with_stdio(false); cin.tie(nullptr);
  cin.exceptions(istream::failbit | istream::badbit);
  cout << fixed << setprecision(15); Calc(); cout.flush(); return 0;
}
template<class A>void amax(A&a, A b) { a = max(a, b); }
template<class A>void amin(A&a, A b) { a = min(a, b); }
template<class A>int comp(A a, A b) { return a < b ? 1 : b < a ? -1 : 0; }
struct Scanner {
  template<class A = string>A Next() { A a; cin >> a; return a; }
  template<class A = int>vector<A>Array(int n) { vector<A>a(n); for (A&i : a) cin >> i; return a; }
  string Line() const { string s; getline(cin, s); return s; }
  template<class A>Scanner&operator,(A&a) { a = Next<A>(); return *this; }
  template<class A>operator A() { return Next<A>(); }
}in;

/*---------------------------------------------------------------------*/

template<class A>void OutContainer(A b, A e, const char *between = " ") {
  if (b != e)while (cout << *b, ++b != e) cout << between;
}
template<class T>void Out(const char* b, const T &t) { cout << t; }
template<class T, class... Args>void Out(const char* b, const T& t, const Args&... args) {
  cout << t << b;
  Out(b, args...);
}
template<class T, class... Args>void OutSpace(const T& t, const Args&... args) { Out(" ", t, args...); }

template<class ...T>tuple<T...>Init(T... t) { return{ t... }; }
template<class T>tuple<T> Init(T t) { return{ t }; }
template<int N, int...I>struct idx_seq : idx_seq<N - 1, 0, (I + 1)...> {};
template<int...I>struct idx_seq<0, I...> {};
template<class R, class T, int...I>R InitInternal(T&&a, idx_seq<0, I...>) { return R{ get<I>(a)... }; }
template<class T, class B, class...V>struct Vec {
  typedef Vec<T, V...>A; typedef vector<typename A::t>t; t nvec(B a, V...b) { return t(a, A().nvec(b...)); }
};
template<class T, class B>struct Vec<T, B> {
  using X = typename conditional<is_same<T, nullptr_t>::value, int, T>::type;
  typedef vector<X>t; t nvec(B a) { return t(a); }
};
template<class T, class ...C>struct Vec<T, tuple<C...>> {
  template<class A, class B>static pair<A, B> X(A, B);
  template<class...A>static tuple<A...> X(A...);
  using t = typename conditional < is_same<T, nullptr_t>::value, decltype(X(C{}...)), T > ::type;
  t nvec(tuple<C...> a) { return InitInternal<t>(a, idx_seq<sizeof...(C)>()); }
};
template<class T, class C>struct Vec<T, tuple<C>> {
  using X = typename conditional<is_same<T, nullptr_t>::value, C, T>::type;
  using t = X; t nvec(tuple<C> a) { return { get<0>(a) }; }
};
template<class T = nullptr_t, class...B> typename Vec<T, B...>::t nvec(B...b) { return Vec<T, B...>().nvec(b...); }

auto v = nvec(0, 0);
vector<int> is;
vector<int> d;
bool dfs(int i) {
  bool isOK = true;
  for (auto& j : v[i]) {
    if (is[j] == false) {
      isOK = false;
      break;
    }
  }
  if (isOK) return true;
  err(i, d);
  for (auto& j : v[i]) {
    if (is[j])continue;
    d.push_back(j + 1);
    is[j] = 1;
    if (dfs(j)) return true;
    is[j] = 0;
    d.pop_back();
  }

  return false;
}

void Calc() {
  var(int, n, m);
  is.resize(n);
  v = nvec(n, 0);
  rep(i, m) {
    var(int, a, b);
    a--, b--;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  int s = 0;
  rep(i, n) {
    if (v[i].size()) {
      s = i;
      is[s] = 1;
      d.push_back(s + 1);
      dfs(i);
      break;
    }
  }
  err(d);
  if (v[s].size() > 1) {
    v[s].erase(std::find(all(v[s]), d[1] - 1));
    reverse(all(d));
    dfs(s);
  }
  assert(d.size());
  cout << (d.size()) << endl;
  OutContainer(all(d));
  cout << endl;
}


Measured memory_bytes: 11512