#include<stdio.h>
#include<list>
using namespace std;
#define nmax 100005
#define mmax 500005
int n, m, i, x, y, inc, sf, ac, urm, nod, nraf;
int gr[nmax], st[mmax], co[nmax];
list <int> ma[nmax];
list <int> ::iterator it;
bool viz[nmax], ok;


void citire()
{
    scanf("%ld %ld",&n,&m);
    for (i=1;i<=m;i++)
    {
        scanf("%ld %ld",&x,&y);
        ma[x].push_back(y);     gr[x]++;
        ma[y].push_back(x);     gr[y]++;
    }
}

void bfs()
{
    co[1]=inc=sf=viz[1]=1;
    while (inc<=sf)
    {
        x=co[inc];  inc++;
        for (it=ma[x].begin();it!=ma[x].end();it++)
            if (!viz[*it])
            {
                co[++sf]=*it;
                viz[*it]=1;
            }
    }
}

void verificare()
{
    ok=1;
    for (i=1;i<=n;i++)
        ok&=viz[i]&(gr[i]%2==0);
}

void sterge_muchia()
{
    ma[ac].erase(ma[ac].begin());
    for (it=ma[urm].begin();it!=ma[urm].end();it++)
        if (*it==ac)
        {   ma[urm].erase(it);  break;       }
}

void extinde()
{
    ac=nod;
    while (1)
    {
        st[++sf]=ac;
        if (ma[ac].size()==0)
            break;
        urm=*ma[ac].begin();
        sterge_muchia();
        ac=urm;
    }
}
void rezolvare()
{
    sf=0;
    st[++sf]=1;
    while (sf>0)
    {
        nod=st[sf]; sf--;
        if (ma[nod].size()>0)
            extinde();
        else
        {
            nraf++;
            if (nraf<=m)
                printf("%ld ",nod);
            else
                break;
        }
    }
}
int main()
{
    freopen("ciclueuler.in","r",stdin);
    freopen("ciclueuler.out","w",stdout);
    citire();
    bfs();
    verificare();
    if (!ok)
        printf("-1\n");
    else
        rezolvare();
    return 0;
}