#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#define nl '\n'

using namespace std;

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

const int NMAX = 5*1e5+1;;

int n, m, fr[NMAX];
vector<int> graph[NMAX];
pair<int,int> edge[NMAX];
stack<int> st, cycle;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        fin >> u >> v;
        edge[i] = {u, v};
        graph[u].push_back(i);
        graph[v].push_back(i);
    }
    bool flag = 1;
    for (int i = 1; i <= n; i++)
        if (graph[i].size()&1)
            flag = 0;
    if (!flag)
    {
        fout << -1;
        return 0;
    }
    st.push(1);
    while (!st.empty())
    {
        int nod = st.top();
        if (graph[nod].size())
        {
            int i = graph[nod].back();
            graph[nod].pop_back();
            if (!fr[i])
            {
                fr[i] = 1;
                int nx = edge[i].first;
                if (nx == nod)
                    nx = edge[i].second;
                st.push(nx);
            }
        }
        else
        {
            st.pop();
            cycle.push(nod);
        }
    }
    while (cycle.size() > 1)
    {
        fout << cycle.top() << ' ';
        cycle.pop();
    }
    return 0;
}