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

using namespace std;

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

const int dim = 1e5 + 5;

struct muchie
{
    int x,y;
    bool anulat;
}e[5*dim];

int n,m;
vector<int> vec[dim],c;
stack<int> st;

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

void Euler()
{
    st.push(1);

    while (!st.empty())
    {
        int x = st.top();
        bool much = 0;

        for (int j=vec[x].size() - 1; j>=0; j--)
        {
            int i = vec[x][j];
            vec[x].pop_back();
            if (!e[i].anulat)
            {
                e[i].anulat = 1;
                int y = (x^e[i].x^e[i].y);
                st.push(y);
                much = 1;
                break;
            }
        }
        if (!much)
        {
            c.push_back(x);
            st.pop();
        }
    }
}

int main()
{
    in >> n >> m;
    for (int i=1; i<=m; i++)
    {
        in >> e[i].x >> e[i].y;
        vec[e[i].x].push_back(i);
        vec[e[i].y].push_back(i);
    }
    if (Pare())
    {
        Euler();
        c.erase(c.begin() + m);
        for (auto x:c) out << x << " ";
    }
    else out << "-1";
    return 0;
}