#include<bits/stdc++.h>
using namespace std;

typedef struct lnod {
    int info;
    lnod *next;
}*nod;

int i,n,m,x,y,grad[100005];
nod lda[100005];

void add(int x,nod &y) {
    nod p=new lnod;
    p->info=x;
    p->next=y;
    y=p;
}

void dfs(int x,int lvl) {
    while(lda[x])
    {
      int aux=lda[x]->info;
      lda[x]=lda[x]->next;
      nod p=lda[aux];
      if(p->info==x) lda[aux]=lda[aux]->next;
      else {
             while(p->next->info!=x) p=p->next;
             p->next=p->next->next;
           }
      dfs(aux,lvl+1);
    }
    if(lvl) printf("%d ",x);
}

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

  for(scanf("%d%d",&n,&m);m;--m)
  {
    scanf("%d%d",&x,&y);
    add(x,lda[y]); ++grad[y];
    add(y,lda[x]); ++grad[x];
  }

  for(i=1;i<=n;++i)
  if(grad[i]&1) return printf("-1\n"),0;

  dfs(1,0);

 return 0;
}