#include <bits/stdc++.h>
#define oo 0x3f3f3f3f 
#define edge pair<int, int>
#define node first
#define number second

using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
int n, m;
vector<edge> graf[100001];
bool edge_viz[500001];
vector<int> result;

void read()
{
  f>>n>>m;
  int x, y;
  for(int i = 1;i <= m;++i)
    f>>x>>y, graf[x].push_back(make_pair(y, i)), graf[y].push_back(make_pair(x, i));
} 

void euler()
{
  for(int i = 1;i <= n;++i)
    if(graf[i].size() & 1)
      {
        g<<-1;
        return;
      }

  memset(edge_viz, false, sizeof(edge_viz));
  stack<int> s;
  s.push(1);

  while(!s.empty())
  {
    int node = s.top();

    if(!graf[node].empty())
    {
      edge e = graf[node].back();
      graf[node].pop_back();

      if(!edge_viz[e.number])
      {
        edge_viz[e.number] = true;
        s.push(e.node);
      }
    }
    else
    {
      s.pop();
      result.push_back(node);
    }
  }
  for(auto it : result)
    g<<it<<" ";

}

int main()
{
  read();
  euler();
  return 0;
}