#include <bits/stdc++.h>

using namespace std;

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

const int Nmax = 5e5 + 5;

int n, m, lg;
int l[Nmax], r[Nmax], sol[Nmax], pos[Nmax];
vector <int> L[Nmax];
bitset <Nmax> viz;

void Dfs(int nod)
{
    while(L[nod].size() > pos[nod])
    {
        int i = L[nod][pos[nod]++];
        if(!viz[i])
        {
            viz[i] = 1;
            Dfs(l[i] + r[i] - nod);
        }
    }

    sol[++lg] = nod;
}

int main()
{
    fin >> n >> m;

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

    for(int i = 1; i <= n; i++)
        if(L[i].size() % 2 == 1)
        {
            fout << -1 << "\n";
            fout.close();
            return 0;
        }

    Dfs(1);

    for(int i = lg; i > 1; i--)
        fout << sol[i] << " ";

    fout.close();
    return 0;
}