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

using namespace std;

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

const int Nmax = 100005;

list<int> A[Nmax];

void solve (int&nod)
{
    while (!A[nod].empty())
    {
        int nod_vecin = A[nod].front();
        A[nod].pop_front();
        A[nod_vecin].erase(find(A[nod_vecin].begin(), A[nod_vecin].end(), nod));
        solve(nod_vecin);
    }
    out << nod << ' ';
}

int main()
{
    int n, m, root = 1;

    in.sync_with_stdio(false);
    in >> n >> m;

    for (int i = 1; i <= m; i++)
    {
        int x, y;
        in >> x >> y;

        A[x].push_back(y);
        A[y].push_back(x);
    }

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

    solve(root);
    return 0;
}