#include <bits/stdc++.h>
#define edge pair<int, int>
#define nod first
#define nr second
 
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
int n, m, x, y;
bool eliminat[500005];
vector<int> rez;
vector<edge> graf[100005];
 
void Read()
{
  f>>n>>m;
  for(int i = 1;i <= m;++i)
    f>>x>>y, graf[x].push_back({y, i}), graf[y].push_back({x, i});
}
 
bool ok()
{
  for(int i = 1;i <= n;++i)
    if(graf[i].size() % 2)
      return false;
  return true;
}

void Solve()
{
  if(!ok()) {g<<-1<<'\n'; return;}
  
  stack<int> v;
  v.push(1);

  while(!v.empty())
  {
    int nod = v.top();

    if(!graf[nod].empty())
    {
      edge muchie = graf[nod].back();
      graf[nod].pop_back();

      if(!eliminat[muchie.nr])
      {
        eliminat[muchie.nr] = true;
        v.push(muchie.nod);
      }
    }
    else
    {
      v.pop();
      rez.push_back(nod);
    }
  }
  for(auto it : rez)
    g<<it<<" ";
}
 
int main()
{
  Read();
  Solve();
  return 0;
}