#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
using namespace std;

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

vector < pair<int,int> > G[100005];
stack <int> st;

int n, m, x, y, i, r, poz, curr, j, vizitat[100005], rez[100005], nxt[500005];

int main()
{
    fin >> n >> m;
    for (i = 1; i <= m; i++)
    {
        fin >> x >> y;
        G[x].push_back({y,i});
        G[y].push_back({x,i});
    }
    for (i = 1; i <= n; i++)
    {
        if ((int)G[i].size() % 2 == 1)
        {
            fout << -1 <<'\n';
            return 0;
        }
    }
    st.push(1);
    while (!st.empty())
    {
        curr = st.top();
        int sz=G[curr].size();
        if (sz > nxt[curr]+1)
        {
            nxt[curr]++;
            int nod_urm = G[curr][nxt[curr]].first;
            int poz_urm= G[curr][nxt[curr]].second;
            if (!vizitat[poz_urm])
            {
                vizitat[poz_urm] = 1;
                st.push(nod_urm);
            }
        }
        else
        {
            st.pop();
            poz++;
            rez[poz] = curr;
        }
    }
    for (i = poz; i >= 1; i--)
        fout << rez[i] << " ";
    return 0;
}