#include <fstream>
#include <vector>

using namespace std;

const int N = 1e5 + 5;
const int M = 5e5 + 5;

int a[M], b[M], grad[N];
vector<int> gr[N], ans;
bool used[M];

void euler(int nod) {
  for (auto muchie : gr[nod])
    if (!used[muchie]) {
      used[muchie] = true;
      int vec;
      if (a[muchie] != nod) vec = a[muchie];
      else vec = b[muchie];
      euler(vec);
    }
  ans.push_back(nod);
}

int main() {
  ifstream cin("ciclueuler.in");
  ofstream cout("ciclueuler.out");
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < m; ++i) {
    cin >> a[i] >> b[i];
    gr[a[i]].push_back(i);
    gr[b[i]].push_back(i);
    ++grad[a[i]], ++grad[b[i]];
  }
  cin.close();
  for (int i = 1; i <= n; ++i)
    if (grad[i] % 2) {
      cout << "-1\n";
      cout.close();
      return 0;
    }
  euler(1);
  ans.pop_back();
  for (auto i : ans)
    cout << i << " ";
  cout.close();
  return 0;
}