#include <bits/stdc++.h>
#define lg 500005

using namespace std;

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

vector<int> L[lg];
int st[lg], dr[lg], poz[lg], sol[lg];
int n, m, p;
bitset<lg> viz;

void Citire()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        fin >> st[i] >> dr[i];
        L[st[i]].push_back(i);
        L[dr[i]].push_back(i);
    }
}

int GradPar()
{
    for(int i = 1; i <= n; i++)
        if(L[i].size() % 2 == 1) return 0;
    return 1;
}

void DfsEuler(int nod)
{
    int l = L[nod].size();
    while(poz[nod] < l)
    {
        int k = L[nod][poz[nod]];
        poz[nod]++;
        if(!viz[k])
        {
            viz[k] = 1;
            DfsEuler(st[k] + dr[k] - nod);
        }
    }
    sol[++p] = nod;
}

void Rezolvare()
{
    if(!GradPar())
    {
        fout << "-1" << "\n";
        exit(0);
    }
    DfsEuler(1);
    for(int i = 1; i <= p; i++)
        fout << sol[i] << " ";
    fout << "\n";
}

int main()
{
    Citire();
    Rezolvare();
    fin.close();
    fout.close();
    return 0;
}