#include <bits/stdc++.h>

using namespace std;
ifstream in("ciclueuler.in");
ofstream out("ciclueuler.out");
const int N = 1e5+1, M = 5e5+1;
vector<int> v[N];
bool viz[M];
int from[M],to[M];

int main()
{
    int n,m;
    in >> n >> m;
    for (int i = 1; i<=m; i++)
    {
        int x,y;
        in >> x >> y;
        v[x].push_back(i);
        v[y].push_back(i);
        from[i] = x;
        to[i] = y;
    }
    for (int i = 1; i<=n; i++)
        if (v[i].size()%2)
        {
            out << "-1";
            return 0;
        }
    stack<int> st;
    vector<int> ans;
    st.push(1);
    while (!st.empty())
    {
        int node = st.top();
        if (!v[node].empty())
        {
            int e = v[node].back();
            v[node].pop_back();
            if (!viz[e])
            {
                viz[e] = 1;
                st.push(from[e]^to[e]^node);
            }
        }
        else
        {
            st.pop();
            ans.push_back(node);
        }
    }
    for (int i = 0; i<ans.size()-1; i++)
        out << ans[i] << " ";
}