#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

using namespace std;

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

const int nmax = 100000;

vector <int> g[nmax + 5], sol;
stack <int> st;
int n, m, grad[nmax + 5];
bool use[nmax + 5];

void Read(){
    fin >> n >> m;
    while (m--){
        int x, y;
        fin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
        grad[x]++; grad[y]++;
    }
}

void DFS(int nod){
    use[nod] = 1;
    for (auto i : g[nod])
        if (!use[i])
            DFS(i);
}

int Check(){
    DFS(1);
    for (int i = 1; i <= n; i++)
        if (grad[i] % 2 || (!use[i] && grad[i]))
            return 0;
    return 1;
}

void Delete(int nod, int vecin){
    g[nod].erase(g[nod].begin());
    for (int i = 0; i < g[vecin].size(); i++)
        if (g[vecin][i] == nod){
            g[vecin].erase(g[vecin].begin() + i);
            return;
        }
}

void Cycle(int nod){
    while (g[nod].size()){
        int vecin = g[nod][0];
        st.push(nod);
        Delete(nod, vecin);
        nod = vecin;
    }
}

void Solve(){
    int nod = 1;
    do{
        Cycle(nod);
        nod = st.top();
        st.pop();
        sol.push_back(nod);
    }while(!st.empty());
}

void Print(){
    for (auto i : sol)
        fout << i << ' ';
    fout << '\n';
}

int main(){
    Read();
    if (!Check()){
        fout << "-1\n";
        return 0;
    }
    Solve();
    Print();
    return 0;
}