#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
#define MAX 100010
typedef vector <int> :: iterator iter;
vector <int> G[MAX];
int viz[MAX], st[5 * MAX], dr, d[MAX], i;
void df(int nod)
{
    if(viz[nod])
        return;
    viz[nod] = 1;
    for(iter it = G[nod].begin() ; it != G[nod].end() ; it++)
        df(*it);
}

void euler(int nod)
{
    while(G[nod].size())
    {
        int v = G[nod][0];
        for(iter it = G[v].begin() ; it != G[v].end() ; it++)
        {
            if(*it == nod)
            {
                G[v].erase(it);
                break;
            }
        }
        G[nod].erase(G[nod].begin());
        euler(v);
    }
    st[++dr] = nod;
}

int main()
{
    int n, m, x, y, ok;
    fin >> n >> m;
    while(m--)
    {
        fin >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
        d[x]++;
        d[y]++;
    }
    df(1);
    ok = 1;
    for(i = 1 ; i <= n ; i++)
    {
        if(d[i] % 2 != 0)
            ok = 0;
        ok &= viz[i];
    }
    if(ok == 0)
    {
        cout << "-1";
        return 0;
    }
    euler(1);
    for(i = 1 ; i < dr ; i++)
    {
        fout << st[i] << " ";
    }
    fout << "\n";
}