#include<bits/stdc++.h>
using namespace std;
const int dim = 1e5 + 55;
int n, m, x, y, grad[dim], solu, p[dim];
vector<pair<int, int > >noduri[dim];
stack<int>stiva;
vector<int>sol;
bitset<5 * dim>viz;
void dfs()
{
    while(!stiva.empty())
    {
        int nod = stiva.top();
        if(grad[nod] == 0)
        {
            sol.push_back(nod);
            stiva.pop();
            continue;
        }
        for(int j = p[nod]; j < noduri[nod].size(); ++j)
        {
            if(!viz[noduri[nod][j].second])
            {
                stiva.push(noduri[nod][j].first);
                viz[noduri[nod][j].second] = 1;
                grad[nod]--;
                grad[noduri[nod][j].first]--;
                p[nod] = j + 1;
                break;

            }
        }
    }
}
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int32_t main(int argc, char * argv[])
{
    fin >> n >> m;
    for(int i = 1; i <= m; ++i)
    {
        fin >> x >> y;
        noduri[x].push_back({y, i});
        noduri[y].push_back({x, i});
        grad[x]++;
        grad[y]++;

    }
    int ok = 1;
    for(int i = 1; i <= n; ++i)
    {
        if(grad[i] % 2)
        {
            ok = 0;
            break;
        }
    }
    if(!ok)
    {
        fout << -1;
        return 0;
    }
    stiva.push(1);
    dfs();
    for(int i = 0; i < sol.size() - 1; ++i)
    {
        fout << sol[i] << " ";
    }
    return 0;
}