#include <iostream>
#include <vector>
#include <stack>
#include <fstream>
#define VMAX 100000
#define EMAX 500000
#define NOTFOUND -1

using namespace std;

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

int V, E, x, y;
vector <int> adj[VMAX];
int deg[VMAX];
int epath[EMAX], lge;
int cpath[EMAX], lgc;

int getIndex(int src, int dest);
void removeEdge(int src, int dest);

int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(0);
    fout.tie(0);

    fin >> V >> E;

    while (E--)
    {
        fin >> x >> y;
        x--, y--;
        adj[x].emplace_back(y);
        adj[y].emplace_back(x);
        deg[x]++, deg[y]++;
    }

    for (int i = 0; i < V; ++i)
        if (deg[i] & 1)
        {
            fout << -1;
            return 0;
        }

    int u, w;
    cpath[lgc++] = 0;
    while (lgc)
    {
        u = cpath[lgc - 1];
        if (adj[u].empty())
        {
            epath[lge++] = u;
            lgc--;
        }
        else
        {
            w = adj[u][0];
            removeEdge(u, w);
            cpath[lgc++] = w;
        }
    }

    for (int i = lge - 1; i >= 1; --i)
        fout << epath[i] + 1 << " ";

    fin.close();
    fout.close();
    return 0;
}

void removeEdge(int src, int dest)
{
    int index = getIndex(src, dest);
    if (index != NOTFOUND)
    {
        E--;
        adj[src].erase(adj[src].begin() + index);
        adj[dest].erase(adj[dest].begin() + getIndex(dest, src));
    }
}

int getIndex(int src, int dest)
{
    for (auto it = adj[src].begin(); it != adj[src].end(); ++it)
        if (*it == dest) return it - adj[src].begin();
    return NOTFOUND;
}