#include <bits/stdc++.h>
#define NMAX 100002
#define MMAX 500002
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

struct muchie
{
    int x,y;
    bool uz;
};
int n,m,poz;
muchie LM[NMAX];
vector<int> LA[NMAX]; ///LA[X] contine indicii muchiilor care il au ca extrmitate pex
int S[MMAX];
int vf;
int sol[MMAX];
void citire();
void determinare_cilcu();
void afisare();
bool grade_pare();
int main()
{
    citire();
    if(!grade_pare()) {fout<<-1<<'\n'; return 0;}
    determinare_cilcu();
    afisare();
    return 0;
}
void citire()
{int i, x, y;
 fin >> n >> m;
 for (i=1; i<=m; i++)
      {
       fin>>x>>y;
       LA[x].push_back(i);
       LA[y].push_back(i);
       LM[i].x=x;
       LM[i].y=y;
       LM[i].uz=0;
      }
}
void determinare_cilcu()
{
    int crt,urm;
    S[1]=1;
    vf=1;
    while(vf>0)
    {
        crt=S[vf];
        if(LA[crt].size()==0)
        {
            sol[++poz]=crt;
            vf--;
        }
        else
        {
            urm=LA[crt].back();
            LA[crt].pop_back();
            if (LM[urm].uz == 0)
                {LM[urm].uz = 1;
                 if (crt ==LM[urm].x)
                     S[++vf]=LM[urm].y;
                     else
                     S[++vf]=LM[urm].x;
                }
        }

    }
}
void afisare()
{
    int i;
    if(poz-1!=m) fout<<-1<<'\n';
      else
      {
          for(i=1;i<=poz-1;i++)
            fout<<sol[i]<<' ';
          fout<<'\n';
      }

}
bool grade_pare()
{
    int i;
    for(i=1;i<=n;i++)
    {
        if(LA[i].size()%2) return 0;
    }
    return 1;
}