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

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

int N, M;

// Algoritm de determinare ciclu euler

// muchie noteaza care muchii au fost vizitate
vector<bool> visitedMuchie;

// u si v sunt vectorii de muchi
// (u[i], v[i]) sunt o muchie
vector<int>u;
vector<int>v;

// vecini pastreaza indicele la aceste muchii
vector<vector<int>> vecini;
vector<int>pos;

// in cycle e creat ciclul
vector<int>cycle;

bool allDegreesEven() {
    for (int i=1;i<=N;i++)
        if (vecini[i].size() % 2 != 0)
            return false;
    return true;
}

void dfs(int nod) {

    // cat timp nod-ul mai are vecini
    // pos[nod] e pozitia la care a ramas nod
    while (pos[nod] < vecini[nod].size()) {
        int current_edge = vecini[nod][pos[nod]++];

        if (!visitedMuchie[current_edge]) {
            visitedMuchie[current_edge] = true;
            dfs(u[current_edge] + v[current_edge] - nod);
        }
    }
    cycle.push_back(nod);
}

int main() {
    fin>>N>>M;

    visitedMuchie.assign(M+1, 0);

    u.assign(M+1, 0);
    v.assign(M+1, 0);

    pos.assign(N+1, 0);

    vecini.resize(N+1);
    for (int i = 1; i <= M; i++) {
        fin>>u[i]>>v[i];
        vecini[u[i]].push_back(i);
        vecini[v[i]].push_back(i);
    }
    if (allDegreesEven()) {
        dfs(1);

        for (int i=cycle.size()-1;i>0;i--)
            fout<<cycle[i]<<" ";
    }
    else {
        fout<<-1;
    }



    return 0;
}