#include <fstream>
#include <vector>
#include <stack>
#define NMAX 100003
#define MMAX 500003
using namespace std;
ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");

struct varf
{
    int x,nr;
};
///x este vf adiacent iar nr numarul muchiei corespunzatoare
int n,m;
vector <varf> G[NMAX];
bool uz[MMAX]; ///uz[i] este 1 daca muchia cu nr de ordin i a fost utilizata pe ciclu
int d[NMAX]; ///gradele
stack <int> stiva;

void citire()
{
    int x,y;
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fin>>x>>y;
        varf vf;
        vf.x=y;
        vf.nr=i;
        G[x].push_back(vf);
        vf.x=x;
        vf.nr=i;
        G[y].push_back(vf);
        d[x]++;
        d[y]++;
    }
}
int grade_pare()
{
    //returneaza 0 daca nu toate gradele sunt pare
    // altfel returneaza indicele unui vf care nu este izolat
    int start;
    for(int i=1; i<=n; i++)
    {
        if(d[i]%2) return 0;
        if(d[i]) start=i;
    }
    return start;
}
void euler(int start)
{
    varf vfad;
    stiva.push(start);
    while(!stiva.empty())
    {
        int vf=stiva.top();
        ///aleg un varf adiacent cu vf
        if(!G[vf].empty())
        {
            vfad=G[vf][G[vf].size()-1];
            if(!uz[vfad.nr])
            {
                stiva.push(vfad.x);
                uz[vfad.nr]=1;
            }
                G[vf].pop_back();
        }
        else {fout<<" "<<vf;stiva.pop();}
    }
}
int main()
{
    citire();
    int start=grade_pare();
    if(!start)
        fout<<-1<<'\n';
    else
    {
        euler(start);
        bool eulerian=1;
        for(int i=1; i<=m && eulerian; i++)
            if(!uz[i]) eulerian=0;
        if(!eulerian)
        {
            fout.close();
            fout.open("ciclueuler.out");
            fout<<-1;

        }
    }
    return 0;
}