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

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

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 solve()
{
  for(int i = 1;i <= n;++i)
    if(graf[i].size() % 2)
      {
        g<<-1;
        return;
      }

  stack<int> s;
  s.push(1);

  while(!s.empty())
  {
    int top = s.top();
    
    if(!graf[top].empty())
    {
      edge e = graf[top].back();
      graf[top].pop_back();

      if(!eliminat[e.number])
        {
          eliminat[e.number] = true;
          s.push(e.nod);
        }
    }
    else
    {
      s.pop();
      result.push_back(top);
    }
  }
  for(int node : result)
    g<<node<<" ";
}

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