#include <fstream>
#include <algorithm>
#include <vector>
#include <stack>
using namespace std;

const int kNMax = 100010;
int n, grad[kNMax], ok;
stack <int> Stack;
vector <int> G[kNMax], sol;

void Citire() {
    ifstream in("ciclueuler.in");
    int m, x, y;
    in >> n >> m;
    for (int i = 1; i <= m; ++i) {
        in >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }
    in.close();
}

void StergereMuchii(int nod, int vecin) {
    G[nod][0] = G[nod][G[nod].size() - 1];
    G[nod].pop_back();
    G[vecin].erase(find(G[vecin].begin(), G[vecin].end(), nod));

}

int ValidareCiclu() {
    for (int i = 1; i <= n; ++i)
        if(grad[i] % 2 == 1)
            return 0;
    return 1;
}

void Solve() {
    ok = ValidareCiclu();
    if (ok) {
        Stack.push(1);
        while (!Stack.empty()) {
            int nod = Stack.top();
            if (G[nod].size()) {
                int vecin = G[nod].front();
                Stack.push(vecin);
                StergereMuchii(nod, vecin);
            } else {
                sol.push_back(Stack.top());
                Stack.pop();
            }
        }
    }
}

void Afisare() {
    ofstream out ("ciclueuler.out");
    if (ok == 0)
        out << -1 ;
    else
        for (int i = 1; i < sol.size(); ++i)
            out << sol[i] << ' ';
    out << '\n';
    out.close();
}

int main() {
    Citire();
    Solve();
    Afisare();
    return 0;
}