#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; ///uz va fi 1 daca mucia a fost folosita pe ciclu
};

int n, m, poz;
muchie LM[MMAX];
vector<int> LA[NMAX];
///LA[x] contine indicii muchiilor care au extremitatea pe x
int S[MMAX];
int vf;
int sol[MMAX];

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

int main()
{
    citire();
    if(!grade_pare()) {fout<<-1<<endl; return 0;}
    determinare_ciclu();
    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);
    }
}

void determinare_ciclu()
{int crt, urm;
    S[1]=1;
    vf=1;
    while(vf>0)
    {
        crt=S[vf]; ///crt ete varful curent
        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;


            }
        }

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

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