#include <fstream>
#include <vector>
#include <list>
using namespace std;
ifstream f("ciclueuler.in");
ofstream g("ciclueuler.out");
vector <int> v[100003];
vector <int> :: iterator it;
list <int> q;
int i,x,y,n,nr,m,of,nod;
int main()
{

    f>>n>>m;
    for (i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    q.push_back(1);
    for (i=1;i<=n;i++)
    {
        if (v[i].size()%2!=0)
        {
            g<<"-1";
            return 0;
        }
    }
    while (!q.empty())
    {
         of=q.front();

         if (v[of].size()==0)
         {
             if (nr<m)
             {
                 g<<of<<" ";
                 nr++;
             }
             q.pop_front();
         }
         else
         {
             nod=v[of].back();
             q.push_front(nod);
             v[of].pop_back();
             for (it=v[nod].begin();it<v[nod].end();it++)
             {
                 if (*it==of)
                 {
                     v[nod].erase(it);
                     break;
                 }
             }
         }
    }
    return 0;
}