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

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

vector <int> G[500005];
stack <int> st;

int n, m, x, y, i, dela[500005], la[500005], 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(i);
        G[y].push_back(i);
        dela[i] = x;
        la[i] = y;
    }
    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 urm = G[curr][nxt[curr]];
            if (!vizitat[urm])
            {
                vizitat[urm] = 1;
                if(curr==dela[urm])
                    st.push(la[urm]);
                else
                    st.push(dela[urm]);
            }
        }
        else
        {
            st.pop();
            poz++;
            rez[poz] = curr;
        }
    }
    for (i = poz; i >= 1; i--)
        fout << rez[i] << " ";
    return 0;
}