#include <fstream>
#include <vector>
using namespace std;

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

pair <int, int> m[500001];
bool okd[100001];
bool ok[500001];

vector <int> v[100001]; //v[x] (x nod) imi va retine de data asta indicii coresp. muchiei
int s[500001], rasp[500001];

void dfs(int r)
{
    okd[r] = 1;
    int i, f;
    for (i = 0; i<v[r].size(); i++)
    {
        f = m[v[r][i]].first ^ m[v[r][i]].second ^ r;
        if (okd[f] == 0)
            dfs(f);
    }
}

int main()
{
    int N, M, i, x, y;
    fin >> N >> M;
    for (i = 1; i<=M; i++)
    {
        fin >> x >> y;
        m[i] = {x, y};
        v[x].push_back(i);
        v[y].push_back(i);
    }
    dfs(1);
    for (i = 1; i<=N; i++)
        if (okd[i] == 0 || v[i].size()&1)
        {
            fout << -1;
            return 0;
        }
    s[0] = s[1] = 1;
    while (s[0] > 0)
    {
        x = s[s[0]];
        if (v[x].empty() == 0)
        {
            y = v[x].back();
            v[x].pop_back();
            if (ok[y] == 0)
            {
                ok[y] = 1;
                y = m[y].first ^ m[y].second ^ x;
                s[++s[0]] = y;
            }
        }
        else
        {
            rasp[++rasp[0]] = x;
            s[0]--;
        }
    }
    for (i = 1; i<rasp[0]; i++)
        fout << rasp[i] << ' ';
    return 0;
}