#include <fstream>
#include <vector>

#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[MMAX];

vector <int> LA[NMAX];

int S[MMAX];
int vf;
int sol[MMAX];

void citire();
bool grade_pare();
void determinare_cicle();
void afisare();

int main()
{
    citire();
    if( !grade_pare() )
        {
        fout<<-1<<'\n';
        return 0;
        }
    determinare_cicle();
    afisare();
    return 0;
}

void citire()
{
    int i, x, y;
    fin>>n>>m;
    for(i=1; i<=m; i++)
    {
        fin>>x>>y;
        LM[i].x=x;
        LM[i].y=y;
        LM[i].uz=0;
        LA[x].push_back(i);
        LA[y].push_back(i);

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

void determinare_cicle()
{
    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(LM[urm].x==crt)
                        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; i++)
                fout<<sol[i]<<' ';
    fout<<'\n';
}