#include <bits/stdc++.h>
using namespace std;

set<int> adj[100005];
vector<int> sol;
stack<int> st;

int main()
{
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);

    int n, m;
    scanf("%d %d", &n, &m);

    for (int i = 0, x, y; i < m; i++) {
        scanf("%d %d", &x, &y);
        //cout << x << " " << y << endl;
        adj[x].insert(y);
        adj[y].insert(x);
    }

    for (int i = 1; i < n; i++) {
            if  (adj[i].size() % 2 != 0) {
                cout << -1 << "\n";
                return 0;
            }
    }

    st.push(1);
    while (!st.empty()) {
        int node = st.top();
        //cout << node << endl;

        if (adj[node].size()) {
            int son = *adj[node].begin();
            //cout << "son: " << son << endl;

            adj[node].erase(adj[node].begin());
            adj[son].erase(adj[son].find(node));

            st.push(son);

        } else {
            sol.push_back(node);
            st.pop();
        }
    }

        for (int i = 0; i < sol.size() - 1; i++) {
            cout << sol[i] << " ";
        }
    cout << "\n";

    return 0;
}