#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream f ("ciclueuler.in");
ofstream g ("ciclueuler.out");
int n,m;
int grade[100001];
pair<int,int> muchii[500001];
stack<int>st;
bool viz[500001];
vector<int>rasp;
vector<int>adiacenta[100001];
void citire()
{
    f >> n >>m;
    for(int i = 1; i<=m; i++)
    {
        int x,y;
        f >> x >> y;
        adiacenta[x].push_back(i);
        adiacenta[y].push_back(i);
        muchii[i] = {x,y};
        grade[x]++;
        grade[y]++;
    }
}
void verificare()
{
    for(int i = 1; i<=n; i++)
        if(grade[i]%2 == 1)
        {
            g<<-1;
            exit(0);
        }
}
void gasire_ciclu()
{
    st.push(1);
    while(!st.empty())
    {
        int curent = st.top();
        if(adiacenta[curent].size()==0)
            {
                rasp.push_back(curent);
                st.pop();
                continue;
            }
        if(viz[adiacenta[curent].back()])
            {
                adiacenta[curent].pop_back();
                continue;
            }
        if(!viz[adiacenta[curent].back()])
        {
            int muchie = adiacenta[curent].back();
            viz[muchie] = 1;
            adiacenta[curent].pop_back();

            if(curent==muchii[muchie].first)
            {
                st.push(muchii[muchie].second);
            }
            else
            {
                st.push(muchii[muchie].first);
            }
        }
    }
}
void afisare()
{
    for(int i = 0;i<rasp.size()-1;i++)
    {
        g<< rasp[i]<< " ";
    }
}
int main()
{
    citire();
    verificare();
    gasire_ciclu();
    afisare();

}