#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

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

int n, m, nodul[500005], k;
vector < int > v[100005];

void sterge_muchie(int x, int y)
{
    for(int i = 0; i < v[y].size(); i++)
        if(v[y][i] == x)
        {
            for(int j = i; j < v[y].size() - 1; j++)
                v[y][j] = v[y][j + 1];
            v[y].pop_back();
            break;
        }
}

void eulerian(int nod)
{
    while(!v[nod].empty())
    {
        int vecin = v[nod].back();
        v[nod].pop_back();
        sterge_muchie(nod, vecin);
        eulerian(vecin);
    }
    nodul[++k] = nod;
}

void citire()
{
    fin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        int x, y;
        fin >> x >> y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
}


int main()
{
    citire();
    for(int i = 1; i <= n; i++)
        if(v[i].size() % 2)
        {
            fout << -1;
            return 0;
        }
    eulerian(1);
    for(int i = k; i >= 2; i--)
        fout << nodul[i] << ' ';

}