#include <bits/stdc++.h>

using namespace std;

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

void usain_bolt()
{
    ios::sync_with_stdio(false);
    fin.tie(0);
}

const int N = 1e5 + 5;

list < int > a[N];
stack < int > st;
vector < int > sol;

int main()
{
    usain_bolt();

    int n, m;

    fin >> n >> m;
    for(int i = 1; i <= m; ++i) {
        int x, y;

        fin >> x >> y;
        a[x].push_back(y);
        a[y].push_back(x);
    }
    for(int i = 1; i <= n; ++i) {
        if(a[i].size() & 1 || a[i].size() == 0) {
            fout << -1;
            return 0;
        }
    }
    st.push(1);
    while(!st.empty()) {
        int x = st.top();
        if(a[x].size() > 0) {
            int v = *a[x].begin();
            list < int > ::iterator it = find(a[v].begin(), a[v].end(), x);
            a[v].erase(it);
            a[x].erase(a[x].begin());
            st.push(v);
        }
        else {
            st.pop();
            sol.push_back(x);
        }
    }
    sol.pop_back();
    for(size_t i = 0; i < sol.size(); ++i) fout << sol[i] << " ";
    return 0;
}