//solutie cu 2 stive
#include <fstream>
#include <vector>
#include <set>
#include <stack>
using namespace std;
const int NMAX = 100001;
const int MMAX = 500001;
vector <int> g[NMAX];
vector <int> sol;
stack <int> stiva;
int grad[NMAX];

int cnt;
bool viz[MMAX];
pair <int, int> cine[MMAX];
int main()
{
    ifstream cin("ciclueuler.in");
    ofstream cout("ciclueuler.out");
    int n, m, i;
    cin >> n >> m;
    for (i = 1; i <= m; i++)
    {
        int a, b;
        cin >> a >> b;
        g[a].push_back(i);
        g[b].push_back(i);
        cine[i] = {a, b};
        grad[a]++;
        grad[b]++;
    }
    bool ok = 0;
    for (i = 1; i <= n; i++)
        if (grad[i] & 1)
        {
            ok = 1;
            break;
        }
    if (ok)
    {
        cout << -1;
        return 0;
    }
    stiva.push(1);
    while (!stiva.empty())
    {
        int f = stiva.top();
        while (!g[f].empty() and viz[g[f].back()])
        {
            g[f].pop_back();
        }
        if (!g[f].empty())
        {
            int ind = g[f].back();
            g[f].pop_back();
            int vecin;
            if (cine[ind].first == f)
            {
                vecin = cine[ind].second;
            }
            else
                vecin = cine[ind].first;
            viz[ind] = 1;
            stiva.push(vecin);
        }
        else
        {
            stiva.pop();
            sol.push_back(f);
        }
    }
    for (i = sol.size() - 1; i > 0; i--)
        cout << sol[i] << ' ';
}