#include<stdio.h>
FILE *f,*g;
long t[4][5000000],c[2000000],fin[2000000],x,y,z,v[5000000],nr,numar,n,m,i;
void ciclu(long k)
{ long p=c[k]; t[3][p]=0; if(p%2==0) t[3][p-1]=0; else t[3][p+1]=0;
  while(p>0)
   {  if(t[3][p])  ciclu(t[1][p]); 
      if(p) p=t[2][p];
   }
  numar++; v[numar]=k;
}
int main()
{ f=fopen("ciclueuler.in","r"); g=fopen("ciclueuler.out","w");
  fscanf(f,"%ld%ld",&n,&m);
  for(i=1;i<=m;i++) 
  { fscanf(f,"%ld%ld",&x,&y); 
    if(c[x]==0) { nr++; c[x]=nr; fin[x]=nr; t[1][nr]=y; t[3][nr]=1; }
	else { nr++; t[2][fin[x]]=nr; t[1][nr]=y; fin[x]=nr; t[3][nr]=1; }
	z=x; x=y; y=z;
	if(c[x]==0) { nr++; c[x]=nr; fin[x]=nr; t[1][nr]=y; t[3][nr]=1;}
	else { nr++; t[2][fin[x]]=nr; t[1][nr]=y; fin[x]=nr; t[3][nr]=1; }
  }
  ciclu(1); 
  if(numar-1==m) for(i=1;i<numar;i++) fprintf(g,"%ld ",v[i]); 
  else fprintf(g,"-1");
  fclose(g);
  return 0;
}