#include <fstream>
#define NMAX 100007
#define MMAX 500007
#include <vector>

using namespace std;

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

struct muchie
{
    int x, y;
    bool uz;///uz va fi 1 daca muchia a fost folosita pe ciclu
};
int n, m;
muchie LM[MMAX];
vector<int> LA[NMAX]; ///LA[x] contine indicii muchiilor care au ca pe extremitate pe x
int S[MMAX];
int vf, poz;
int sol[MMAX];

void citire();
void determinareciclu();
bool pare();
void afisare();

int main()
{
    citire();
    determinareciclu();
    if (!pare())
    {
        fout << -1;
        return 0;
    }
    afisare();
    return 0;
}

void citire()
{
    int x, y;
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        fin >> x >> y;
        LM[i].x = x;
        LM[i].y = y;
        LM[i].uz = 0;
        LA[x].push_back(i);
        LA[y].push_back(i);
    }
}

void determinareciclu()
{
    int crt, urm;
    S[1] = 1;
    vf = 1;
    while (vf > 0)
    {
        crt = S[vf];
        if (LA[crt].size() == 0)
        {
            sol[++poz] = crt;
            vf--;
        }
        else
        {
            urm = LA[crt].back();
            LA[crt].pop_back();
            if (LM[urm].uz == 0)
            {
                LM[urm].uz = 1;
                if (LM[urm].x == crt) S[++vf] = LM[urm].y;
                else S[++vf] = LM[urm].x;
            }
        }
    }
}

bool pare()
{
    for (int i = 1; i <= n; i++)
        if (LA[i].size()%2 == 1) return 0;
    return 1;
}

void afisare()
{
    if ((poz-1) != m) fout << -1;
    else
        for (int i = 1; i < poz; i++)
            fout << sol[i] << ' ';
}