#include<stdio.h>
FILE *f,*g;
int t[4][2000000],c[200000],fin[200000],x,y,z,v[2000000],nr,numar,n,m,i,viz[200000],grad[200000],ok;
inline  void ciclu(long k)
{ int p=c[k]; if(grad[k]%2==0) {
  while(p&&numar<=m+10)
   {  if(!t[3][p]) { t[3][p]=1; if(p%2==0) t[3][p-1]=1; else t[3][p+1]=1; ciclu(t[1][p]); }
      p=t[2][p];
   }
  numar++; v[numar]=k; } else ok=0;
}
int main()
{ f=fopen("ciclueuler.in","r"); g=fopen("ciclueuler.out","w");
  fscanf(f,"%d%d",&n,&m);
  for(i=1;i<=m;i++)
   { fscanf(f,"%d%d",&x,&y); 
     if(c[x]==0) { nr++; c[x]=nr; fin[x]=nr; t[1][nr]=y; grad[x]++; }
	 else { nr++; t[2][fin[x]]=nr; t[1][nr]=y; fin[x]=nr; grad[x]++;}
	 z=x; x=y; y=z;
	 if(c[x]==0) { nr++; c[x]=nr; fin[x]=nr; t[1][nr]=y; grad[x]++;}
	 else { nr++; t[2][fin[x]]=nr; t[1][nr]=y; fin[x]=nr; grad[x]++;}
   }
   
  ok=1; ciclu(1);
  if(numar-1==m&&ok) for(i=1;i<numar;i++) fprintf(g,"%d ",v[i]); else fprintf(g,"-1");
  fclose(g);
  return 0;
}