#include<stdio.h>
#include<stdlib.h>
#define N 100001
#define M 500001
typedef struct stack
{long st[N],sp;};
typedef struct nod
{long info;
nod *next;}Nod,*list;
long a[M],b[M],i,j,k,n,m,s[N]={0},t,u,c[M]={0},r,p[N],w,v;
list g[N];
stack q;

void push(stack &q,long x)
{q.st[++q.sp]=x;}

long pop(stack &q)
{return q.st[q.sp--];}

void add(list &q,long x)
{Nod *nou=new Nod;
nou->info=x;
nou->next=q;
q=nou;}

int contine(list &q,long x)
{Nod *p;
for(p=q;p!=NULL;p=p->next)
if(p->info==x)
      return 1;
return 0;}

void del(list &l,long x)
{Nod *p=l,*q=l;
while(p!=NULL&&p->info!=x)
      {q=p;
      p=p->next;}
if(p!=NULL)
      {if(q==p)
             l=l->next;
      else
             q->next=p->next;
      free(p);}}
     
int grade_pare(list g[N],long n)
{long i=1,s=0;
list p;
int gasit=0;
while(i<=n&&!gasit)
      {for(p=g[i];p!=NULL;p=p->next)
             s++;
      if(s%2==1)
             gasit=1;
      i++;}
return (!gasit);}

void df(list g[N],long i)
{long j;
list p;
stack q;
q.sp=0;
push(q,i);
while(q.sp!=0)
       {j=pop(q);
       s[j]=1;
       for(p=g[j];p!=NULL;p=p->next)
       if(s[p->info]==0)
              push(q,p->info);}}

int conex(list g[N],long s[N])
{long i;
int gasit=0;
df(g,1);
for(i=1;i<=n;i++)
if(s[i]==0)
      gasit=1;
return (!gasit);}

int main()
{freopen("ciclueuler.in","r",stdin);
freopen("ciclueuler.out","w",stdout);
scanf("%ld%ld\n",&n,&m);
for(j=1;j<=n;j++)
      {g[j]=NULL;
      p[j]=0;}
for(i=1;i<=m;i++)
      {scanf("%ld%ld\n",&a[i],&b[i]);
      add(g[a[i]],b[i]);
      add(g[b[i]],a[i]);}
if(conex(g,s)==1&&grade_pare(g,n)==1)
      {q.sp=0;
      r=0;
      w=0;
      v=0;
      push(q,1);
      while(q.sp!=0)
            {if(v<m)
                   {j=pop(q);
                   printf("%ld ",j);
                   v++;}
            else
                   break;
            w=r;
            u=0;
            for(k=m;k>=1;k--)
            if(c[k]==0&&(a[k]==j||b[k]==j))
                   {r=k;
                   c[r]=1;
                   if(a[k]==j)
                          {p[b[k]]=j;
                          push(q,b[k]);}
                   else
                          {p[a[k]]=j;
                          push(q,a[k]);}
                   del(g[a[k]],b[k]);
                   del(g[b[k]],a[k]);
                   break;}
            else
                   if(c[k]==1)
                           u++;
            if(u==m&&((p[j]==a[r]&&b[r]==j)||(p[j]==b[r]&&a[r]==j)))
                   {if(a[k]==j)
                           push(q,b[k]);
                   else
                           push(q,a[k]);
                   break;}}}            
else
      printf("-1");
fclose(stdin);
fclose(stdout);
return 0;}