#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;
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;}

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;
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;
      u=0;
      r=0;
      push(q,1);
      while(q.sp!=0)
            {j=pop(q);
            if(u<m)
                   {printf("%ld ",j);
                   u++;}
            for(k=1;k<=m;k++)
            if(c[k]==0&&(a[k]==j||b[k]==j))
                   {t=0;
                   if(r!=0&&((a[r]==a[k]&&b[r]==b[k])||(a[r]==b[k]&&b[r]==a[k])))
                           t=1;
                   if(t==0)
                           {c[k]=1;
                           r=k;
                           if(a[k]==j)
                                 push(q,b[k]);
                           else
                                 push(q,a[k]);
                           del(g[a[k]],b[k]);
                           del(g[b[k]],a[k]);}}}}
else
      printf("-1");
fclose(stdin);
fclose(stdout);
return 0;}