#include <iostream>
#include <fstream>
#include <vector>
#include <array>
#include <stack>
#include <algorithm>
using namespace std;

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

const int NMAX = 1e5 + 1;
const int MMAX = 5e5 + 1;
bool sters[MMAX];

array<vector<int>, NMAX> lista;
int from[NMAX], to[NMAX];

int main()
{
    int i, j, n, m, x, y;
    fin>>n>>m;
    for(i=0; i<m; i++)
    {
        fin>>x>>y;
        lista[x].push_back(i);
        lista[y].push_back(i);
        from[i] = x;
        to[i] = y;
    }

    auto e_impar = [](const vector<int>& v)
    {
        return (v.size()%2);
    };

    int nr_imp = count_if(lista.begin(), lista.end(), e_impar);
    if(nr_imp != 0)
    {
        fout<<"-1\n";
        fin.close();
        fout.close();
        return 0;
    }

    vector<int> rez;
    stack<int> st;
    int nod;
    st.push(1);

    while(!st.empty())
    {
        nod = st.top();
        if(!lista[nod].empty())
        {
            int e = lista[nod].back();
            lista[nod].pop_back();
            if(!sters[e])
            {
                int dest = to[e] ^ from[e] ^ nod;
                sters[e] = true;
                st.push(dest);
            }
        }
        else
        {
            rez.push_back(nod);
            st.pop();
        }
    }

    for(i=0; i<rez.size() - 1; i++)
    {
        fout<<rez[i]<<' ';
    }

    fin.close();
    fout.close();
    return 0;
}