# include <stdio.h>
int s[100001],i,j,n,m,x,y,k,ok,sf,k2;
struct nod
{
int info;
nod *urm;
}*a[100001],*p=NULL,*v=NULL,*z=NULL,*q=NULL,*w=NULL;

void df (int x)
{
nod *p;
s[x]=1;
p=a[x];
  while (p)
  {
   if (s[p->info]==0)
   df (p->info);
   p=p->urm;
  }
}



void ciclu ()
{

  while (q)
   {
   k2=q->info;
    p=a[k2];


   if (p)
   {
    k=p->info;

    v=new nod;
    v->info=k;
    v->urm=q->urm;
    q->urm=v;



    a[k2]=a[k2]->urm;



  p=a[k];
 if (a[k]->info==k2)
  {

   a[k]=a[k]->urm;

   }
 else
  {
  while (p->urm->urm)
  {

   if (p->urm->info==k2)
   {
    v=p->urm;
    p->urm=v->urm;

   }
   if (p)
   p=p->urm;
  }
  if (p)
  if (p->urm->info==k2)
  p->urm=0;

 }


}


q=q->urm;
}
}


int main ()
{
freopen ("ciclueuler.in","r",stdin);
freopen ("ciclueuler.out","w",stdout);
for (i=1;i<=n;i++)
a[i]=NULL;
scanf ("%i%i",&n,&m);


for (i=1;i<=m;i++)
{
scanf ("%i%i",&x,&y);
p=new nod;
p->info=x;
p->urm=a[y];
a[y]=p;
p=new nod;
p->info=y;
p->urm=a[x];
a[x]=p;
}


for (i=1;i<=n;i++)
{
k=0;
p=a[i];
while (p)
{
k++;
p=p->urm;
}
if (k%2==1)
ok=1;
}
df (1);
for (i=1;i<=n;i++)
if (s[i]==0)
ok=1;



if (ok==1)
printf ("-1");

   else
   {

z=new nod;
z->info=1;
z->urm=0;
w=z;

   while (z)
   {
    q=z;
    ciclu ();
    z=z->urm;
   }

 z=w;

   while (z->urm)
    {
     printf ("%i ",z->info);
     z=z->urm;
    }



    }
return 0;
}