#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[NMAX];
vector <int> LA[NMAX];
int s[NMAX];
int sol[NMAX];
int vf;

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

int main()
{
    citire();
    if(!grade_pare()){
        fout << -1 << '\n';
        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[y].y=y;
        LM[i].uz=0;
        LA[x].push_back(i);
        LA[y].push_back(i);
    }
}

void determinare_ciclu(){
    int crt, poz, 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;
            }
          }
    }
}

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

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