#include <bits/stdc++.h>
// #define in cin
// #define out cout

using namespace std;

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

const int nmax = 1e5 + 5e0;

struct muchie
{
    int a, b;
    bool viz;
    muchie(int a, int b) : a(a), b(b)
    {
        viz = 0;
    }
    int nxt(int val)
    {
        return a ^ b ^ val;
    }
};

vector<muchie *> adj[nmax];

vector<int> ans;

void dfs(int nod)
{
    while (!adj[nod].empty())
    {
        auto m = adj[nod].back();
        adj[nod].pop_back();
        if (m->viz == 0)
        {
            m->viz = 1;
            dfs(m->nxt(nod));
        }
    }

    ans.push_back(nod);
}

int main()
{
    int n, m;
    in >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int a, b;
        in >> a >> b;
        auto tmp = new muchie(a, b);
        adj[a].push_back(tmp);
        adj[b].push_back(tmp);
    }
    for (int i = 1; i <= n; i++)
    {
        if (adj[i].size() % 2 == 1)
        {
            out << -1;
            return 0;
        }
    }
    dfs(1);
    ans.pop_back();
    for (auto i : ans)
        out << i << ' ';
}