#include <fstream>
#include <vector>
#include <list>
#include <algorithm>
#include <stack>

#define NMAX 100005

using namespace std;

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

int n, m;
stack<int> S;
vector<int> sol;
vector<int> G[NMAX];

int eulerian()
{
    for (int i = 1; i <= n; ++i)
        if (G[i].size() & 1) return 0;
    return 1;
}
void euler()
{
    int x, y;

    S.push(1);
    while (!S.empty())
    {
        x = S.top();

        if (!G[x].empty())
        {
            y = *(G[x].rbegin());
            G[x].pop_back();

            G[y].erase(find(G[y].begin(),G[y].end(), x));

            S.push(y);
        }
        else
        {
            sol.push_back(x);
            S.pop();
        }
    }

}
int main()
{
    int x, y;
    fin >> n >> m;

    for (int i = 1; i <= m; ++i)
    {
        fin >> x >> y;
        G[x].push_back(y);
        G[y].push_back(x);
    }

    if (eulerian())
    {
        euler();
        sol.pop_back();
        for (int i = 0; i < sol.size(); ++i)
            fout << sol[i] << ' ';

    }
    else fout << "-1" << '\n';
    return 0;
}