#include <fstream>
#include <vector>
#include<stack>
#define NMAX 100002
#define MMAX 500002
using namespace std;
ifstream fin ("ciclueuler.in");
ofstream fout ("ciclueuler.out");

struct varf
{
    int x,nr;
};// x e vf diacent iar nr e nr muchiei coresp;
int n,m;
vector<varf> G[NMAX];
bool uz[MMAX]; // uz[i]=1, daca muchia cu nr de ordine i a fost utilizata pe ciclu
int d[NMAX];
stack<int> S;

void citire();
int gradepare();
void euler(int start);

int main()
{
    int start,eulerian,i;
    citire();
    if(!(start=gradepare()))
        fout<<-1<<'\n';
    else
    {
        euler(start);
        eulerian=1;
        for(i=1; i<=m; i++)
            if(!uz[i]) eulerian=0;
        if(!eulerian)
        {
            fout.close();
            fout.open("fleury.out");
            fout<<-1<<'\n';
        }
    }
    return 0;
}
void citire()
{
    varf vf;
    int i,x,y;
    fin>>n>>m;
    for(i=1; i<=m; i++)
    {
        fin>>x>>y;
        //y intra in lita de adiacenta a lui x
        vf.x=y;
        vf.nr=i;
        G[x].push_back(vf);
        //x intra in lita de adiacenta a lui y
        vf.x=x;
        vf.nr=i;
        G[y].push_back(vf);
        d[x]++;
        d[y]++;
    }
}
int gradepare()
{
    int i, start;
    //return 0, daca nu toate gradele sunt pare
    for(i=1; i<=n; i++)
    {
        if(d[i]%2) return 0;
        if(d[i]) start=i;
    }
    return start;
}
void euler (int start)
{
    varf vfad;
    int vf;
    S.push(start);
    while (!S.empty())
    {
        vf=S.top();
        //aleg un vf adiacent cu vf
        if(!G[vf].empty())
        {
            vfad=G[vf][G[vf].size()-1];
            if(!uz[vfad.nr]) // muchie neutilizata
            {
                uz[vfad.nr]=1;
                S.push(vfad.x);
            }
            G[vf].pop_back();
        }
        else {fout<<' '<<vf; S.pop();}
    }
}