#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#define DM 100005
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

int n, m, a, b, used[DM * 5], top;
vector <pair<int, int> > g[DM]; // retinem si muchia
pair<int, int> act;

void parcurgere_euler(int nod)
{

    while(g[nod].size())
    {
        act = g[nod].back();
        g[nod].pop_back();
        if(!used[act.second])
        {
            used[act.second] = 1;
            parcurgere_euler(act.first);
        }
        //g[act].erase(find(g[act].begin(), g[act].end(), nod));
    }
    cout << nod << ' ';
}



int main()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        fin >> a >> b;
        g[a].push_back({b, i});
        g[b].push_back({a, i});
    }

    for(int i = 1; i <= n; i++)
        if(g[i].size() % 2 != 0)
        {
            fout<<"-1";
            return 0;
        }

    parcurgere_euler(1);

    return 0;
}