#include <algorithm>
#include <fstream>
#include <vector>
#include <iostream>
#define SZ(x) ((int) (x).size())
using namespace std;

const int NMAX = 100005, MMAX = 500005;

vector<int> G[NMAX];
struct muchie {int from, to;} VM[MMAX];
bool usedEdge[MMAX];
//int from[MMAX], to[MMAX];

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

    int n, m;
    fin >> n >> m;
///Atentie la memorarea vecinilor si a muchiilor
    for (int i = 0; i < m; ++i) {
        int x, y;
        fin >> x >> y;
        G[x].push_back(i);
        G[y].push_back(i); ///Retine pozitia muchiei in vectorii muchiilor
        //from[i] = x;
        VM[i].from = x; VM[i].to=y;
        //to[i] = y;
    }

    for (int i = 1; i <= n; ++i) {
        if (SZ(G[i]) & 1) {
            fout << "-1\n";
            return 0;
        }
    }

    vector<int> ans; int to;

    vector<int> stk;
    stk.push_back(1);
    while (!stk.empty()) {
        int node = stk.back();//cout<<node<<"k";
        if (!G[node].empty()) {
            int e = G[node].back();///scoate pozitia
            G[node].pop_back();
            if (!usedEdge[e]) {
                usedEdge[e] = true;
                //cout <<from[e]<<"-"<<to[e]<<": ";
               // cout <<VM[e].from<<"-"<<VM[e].to<<": ";
                if(VM[e].from==node)
                    to= VM[e].to;
                else
                   to =VM[e].from;
               // int to = ::from[e] ^ ::to[e] ^ node;
               // int to = ::from[e]  ;
                stk.push_back(to);

                 }
        } else {
            stk.pop_back();
            ans.push_back(node);
        }
    }

    for (int i = 0; i < SZ(ans) - 1; ++i) {
        fout << ans[i] << ' ';
    }
    fout << '\n';

    fin.close();
    fout.close();
}