#include <fstream>
#include <vector>
using namespace std;
ifstream fi ("ciclueuler.in");
ofstream fo ("ciclueuler.out");
vector<pair<int,int>> v[100005];
struct nod{
int val;
nod *ant,*urm;
nod()
{
    val=0;
    ant=NULL;
    urm=NULL;
}
}*cap,*coada,*poz;
int idx[100005],viz[500006];
int nrnod,nrmuchii;
int main()
{
    fi>>nrnod>>nrmuchii;
    for (int i=1;i<=nrmuchii;i++)
    {
        int x,y;
        fi>>x>>y;
        v[x].push_back(make_pair(y,i));
        v[y].push_back(make_pair(x,i));
    }
    for (int i=1;i<=nrnod;i++)
        if (v[i].size()%2==1)
    {
        fo<<-1;
        return 0;
    }
    cap=new nod;coada=new nod;poz=new nod;
    cap->urm=poz;
    poz->urm=coada;
    coada->ant=poz;
    poz->ant=cap;
    poz->val=1;
    while (poz!=cap)
    {
        int valcur=poz->val;
        if (idx[valcur]==v[valcur].size())
        {
            poz=poz->ant;
            continue;
        }
        if (viz[v[valcur][idx[valcur]].second]) {idx[valcur]++;continue;}
        viz[v[valcur][idx[valcur]].second]=1;
        int valurm=v[valcur][idx[valcur]].first;
        nod *pozurm=new nod;

        pozurm->urm=poz->urm;
        pozurm->ant=poz;
        poz->urm->ant=pozurm;
        poz->urm=pozurm;
        pozurm->val=valurm;

        idx[valcur]++;
        poz=pozurm;
    }
    poz=cap->urm;
    while (poz!=coada->ant)
    {
        fo<<poz->val<<' ';
        poz=poz->urm;
    }
    return 0;
}