#include <fstream>
#include <vector>
#include <queue>

using namespace std;

ifstream in ("ciclueuler.in");
ofstream out ("ciclueuler.out");

const int N = 100009;

struct Muchie {
  int first;
  int second;
};

Muchie getMuchie (int x, int y)
{
  Muchie m;
  m.first = x;
  m.second = y;
  return m;
}

int noduri, muchii;

vector <int> indici[N*5];

bool folosit[N*5];

vector <int> ciclu;

bool vizitat[N*5];

Muchie v[N*5];

queue <int> coada;

void read()
{
  in >> noduri >> muchii;

  for (int i = 1; i <= muchii; ++i) {
    int x, y;
    in >> y >> x;

    indici[x].push_back(i);
    indici[y].push_back(i);

    v[i] = getMuchie(x, y);
  }
}

inline int varf (int nod, int valoare)
{
  if (v[nod].first == valoare) {
    return v[nod].second;
  }
  return v[nod].first;
}

inline void euler (int x)
{

  for (vector<int>::iterator it = indici[x].begin(); it < indici[x].end(); ++it) {
    int indice = *it;
    if (!folosit[indice]) {
      folosit[indice] = true;
      //out << "nod = " << indice << "\n";
      //out << "valoare = " << x << "\n\n";
      int y = varf(indice, x);
      euler(y);
    }
  }
  ciclu.push_back(x);
}

void bfs (int sursa)
{
  coada.push(sursa);

  while(!coada.empty()) {
    int curent = coada.front();
    coada.pop();
    for (vector<int>::iterator it = indici[curent].begin(); it < indici[curent].end(); ++it) {
      int fiu = *it;
      if (!vizitat[fiu]) {
            vizitat[fiu] = true;
            coada.push(fiu);
      }
    }
  }
}

void dfs (int x)
{
  vizitat[x] = true;

  //out << "x = " << x << "\n";

  for (vector<int>::iterator it = indici[x].begin(); it < indici[x].end(); ++it) {
    int y = varf(*it, x);
    //out << "y = " << y << "\n\n";
    if (!vizitat[y]) {
      dfs(y);
    }
  }
}

bool check ()
{
  dfs(1);

  //bfs(1);

  //out << "Sunt in check\n";

  for (int i = 1; i <= noduri; ++i) {
    if (!vizitat[i] or indici[i].size() % 2) {
      return false;
    }
  }
  return true;
}



void solve ()
{
  //modificaStiva();
  bool ok = check();
  //out << "ok = " << ok << "\n";

  if (!ok) {
    out << "-1\n";
    return;
  }


  euler(1);

  //out << elementeCiclu << "\n";

  //out << "size = " << ciclu.size() << "\n";

  if (ciclu.size() == muchii + 1) {
    for (int i = 0; i < muchii; ++i) {
      out << ciclu[i] << " ";
    }
    out << "\n";
  } else {
    out << "-1\n";
  }
}

int main()
{
  read();
  solve();

  return 0;
}