# include <stdio.h>
int s[100001],i,j,n,m,x,y,k,ok,eul[501],sf,k2;
struct nod
{
int info;
nod *urm;
}*a[100001],*p,*v;

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 (int ind)
{
k2=eul[ind];
p=a[k2];

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

sf++;
for (j=sf;j>ind;j--)
eul[j]=eul[j-1];
ind++;
eul[ind]=k;

a[k2]=p->urm;
delete p;
p=a[k];

if (p->info==k2)
{
a[k]=p->urm;
delete p;
}
else
{
while (p->urm)
{
if (p->urm->info==k2)
{
v=p->urm;
p->urm=v->urm;
delete v;
break;
}
p=p->urm;
}

}
ciclu (eul[ind]);


}

}



int main ()
{
freopen ("ciclueuler.in","r",stdin);
freopen ("ciclueuler.out","w",stdout);
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
{
eul[1]=1;
sf=1;
for (i=1;i<=m;i++)
ciclu (i);
for (i=1;i<=sf-1;i++)
printf ("%i ",eul[i]);
}
return 0;
}