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

#define pb push_back
#define pp pop_back
#define DIM 100005

int sol[DIM],grd[DIM],viz[DIM];
vector <int> lst[DIM];
int n,m,nrt;

void read ()
{
    int i,x,y;

    scanf ("%d%d",&n,&m);
    for (i=1; i<=m; ++i)
    {
        scanf ("%d%d",&x,&y);
        ++grd[x];
        ++grd[y];
        lst[x].pb (y);
        lst[y].pb (x);
    }
}

void df (int nod)
{
    int i;

    viz[nod]=1;
    for (i=0; i<(int)lst[nod].size (); ++i)
        if (!viz[lst[nod][i]])
            df (lst[nod][i]);
}

int check ()
{
    int i;

    for (i=1; i<=n; ++i)
        if (grd[i]&1)
            return 0;
    df (1);
    for (i=1; i<=n; ++i)
        if (!viz[i])
            return 0;
    return 1;
}

void euler (int nod)
{
    int i,next,prev;

    for ( ; (int)lst[nod].size (); )
    {
        next=lst[nod][(int)lst[nod].size ()-1];
        lst[nod].pp ();
        for (i=0; i<(int)lst[next].size (); ++i)
            if (lst[next][i]==nod)
            {
                prev=i;
                break;
            }
        lst[next][prev]=lst[next][(int)lst[next].size ()-1];
        lst[next].pp ();
        euler (next);
    }
    sol[++nrt]=nod;
}

void solve ()
{
    int i;

    if (check ())
    {
        euler (1);
        for (i=1; i<nrt; ++i)
            printf ("%d ",sol[i]);
    }
    else
        printf ("-1");
}

int main ()
{
    freopen ("ciclueuler.in","r",stdin);
    freopen ("ciclueuler.out","w",stdout);

    read ();
    solve ();

    return 0;
}