//
//  main.cpp
//  ciclu eulerian infoarena
//
//  Created by Razvan Vranceanu on 04/03/2020.
//  Copyright © 2020 Razvan Vranceanu. All rights reserved.
//

//#include "/Users/razvanvranceanu/stdc++.h"
#include <bits/stdc++.h>
#define MAX 100100
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");

list<int> g[MAX];
vector<int> sol;

int n,m;

void citire(int &n, int &m)
{
    fin>>n>>m;
    int x, y;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        g[x].push_back(y);
        g[y].push_back(x);
    }
}
void euler(int node)
{
    int vecin;
    while(!g[node].empty())
    {
        vecin = g[node].front();
        g[node].pop_front();
        g[vecin].erase(find(g[vecin].begin(), g[vecin].end(), node));
        euler(vecin);
    }
    sol.push_back(node);
}
int main()
{
    citire(n, m);
    
    for(int i=1;i<=n;i++)
        if(g[i].size()%2)
        {
            fout<<-1;
            return 0;
        }
    euler(1);
    for(int i=1;i<=sol.size()-1;i++)
        cout<<sol[i]<<" ";
    return 0;
}