#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#define pii pair<int, int>
using namespace std;

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

const int NMAX = 1e5 + 5, MMAX = 5e5 + 5;

vector<pii> g[NMAX];
int visitat[MMAX], poz[NMAX];
int main () {
    int n, m;
    fin >> n >> m;
    int x,y, id = 0;

    for (int i = 0; i < m; i++) {
        fin >> x >> y;
        g[x].push_back({y, id});
        g[y].push_back({x, id});
        id++;
    }

    for (int i = 1; i <= n; i++) {
        if(g[i].size() % 2 == 1) {
            fout << -1;
            return 0;
        }
    }


    stack<int> st;
    vector<int> ciclu;

    st.push(1);
    while (!st.empty()) {
        int nod = st.top();
        
        int ok = 0;
        while (poz[nod] < g[nod].size()) {
            pii neigh = g[nod][poz[nod]++];
            if (visitat[neigh.second] == 0) {
                visitat[neigh.second] = 1;
                st.push(neigh.first);
                ok = 1;
                break;
            }
        }
        if (ok == 0) {
            ciclu.push_back(nod);
             st.pop();
        }
    }

    for (auto it: ciclu) {
        fout << it << " ";
    }



}