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

const int N_MAX = 100010;
const int M_MAX = 500010;

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

struct mch
{
    int a,b;
};

int n,m;
mch muchie[M_MAX];
bool vizitat[M_MAX];
vector<int> muchie_nod[N_MAX];
int stiva[M_MAX]; int n_stiva;
int grad[N_MAX]={0};
int sol[M_MAX]; int n_sol=0;

void citeste()
{
    int x,y;
    //freopen("ciclueuler.in","r",stdin);
    //freopen("ciclueuler.out","w",stdout);
    //scanf("%d%d",&n,&m);
    in>>n>>m;
    for (int i = 1; i <= m; ++i)
    {
        //scanf("%d%d",&x,&y);
        in>>x>>y;
        muchie[i] = (mch){x,y};
        muchie_nod[x].push_back(i);
        ++grad[x];
        muchie_nod[y].push_back(i);
        ++grad[y];
        vizitat[i] = false;
    }
}

bool graf_eulerian()
{
    for (int i = 1; i <= n; ++i)
        if (grad[i] % 2 == 1)
            return false;
    return true;
}

void ciclu_eulerian()
{
    stiva[++n_stiva] = 1;
    int nod; int mch_sel;
    unsigned int i;
    while (n_stiva > 0)
    {
        nod = stiva[n_stiva];
        for (i = 0; i < muchie_nod[nod].size(); ++i)
        {
            mch_sel = muchie_nod[nod][i];
            if (!vizitat[mch_sel])
            {
                vizitat[mch_sel] = true;
                if (muchie[mch_sel].a == nod)
                    stiva[++n_stiva] = muchie[mch_sel].b;
                else
                    stiva[++n_stiva] = muchie[mch_sel].a;
                break;
            }
        }
        if (i == muchie_nod[nod].size())
        {
            sol[++n_sol] = nod;
            --n_stiva;
        }
    }
}

void scrie()
{
    for (int i = n_sol; i >= 2; --i)
        out<<sol[i]<<" "; //printf("%d ",sol[i]);
}

int main()
{
    citeste();
    if (graf_eulerian())
    {
        ciclu_eulerian();
        scrie();
    }
    else
        out<<-1;//printf("-1\n");
    out<<"\n";
    return 0;
}