#include <fstream>
#include <vector>
#include <stack>
using namespace std;

ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

const int NMAX=100010;

int n,m;
int grad[NMAX];
stack<int>sol;
stack<int>stiva;
vector<int>lista[NMAX];
bool eulerian=true;
struct muchie{
    int x,y;
    bool folosit;
}muchii[5*NMAX];
void citire()
{
    fin>>n>>m;
    int a,b;
    for (int i=1; i<=m; i++){
        fin>>a>>b;
        muchii[i].x=a;
        muchii[i].y=b;
        muchii[i].folosit=false;
        grad[a]++;
        grad[b]++;
        lista[a].push_back(i);
        lista[b].push_back(i);
    }
}
void ciclu(int start)
{
    stiva.push(start);
    int i,j;
    while (!stiva.empty()){
        i=stiva.top();
        if (grad[i]!=0){
            int muchie=lista[i].back();
            lista[i].pop_back();
            while (muchii[muchie].folosit){
                muchie=lista[i].back();
                lista[i].pop_back();
            }
            muchii[muchie].folosit=true;
            j=(muchii[muchie].x==i?muchii[muchie].y:muchii[muchie].x);
            grad[i]--;
            grad[j]--;
            stiva.push(j);
        }else{
            sol.push(i);
            stiva.pop();
        }
    }
}
void rezolvare()
{
    for (int i=1; i<=n; i++){
        if (grad[i]%2!=0){
            eulerian=false;
            return;
        }
    }
    ciclu(1);
}
void afisare()
{
    if (!eulerian){
        fout<<-1<<'\n';
    }
    while (sol.size()>1){
        fout<<sol.top()<<' ';
        sol.pop();
    }
}
int main()
{
    citire();
    fin.close();
    rezolvare();
    afisare();
    fout.close();
    return 0;
}