Program ciclueuler;
 type lista=^celula;
    celula=record
          nod,c:longint;
          next:lista;
          end;
var g:array [1..100001] of lista;
    v:lista;
    b1,b2:array [1..1 shl 17] of char;
    aux:array [1..100001] of longint;
    i,j,n,m,x,y,nr:longint;
    ok:boolean;
    b:array [1..100001] of longint;
    fi,fo:text;
procedure introdu(x,y:longint);
begin
 v:=g[x];
  while v<>nil do begin
   if v^.nod=y then begin inc(v^.c); break; end;
    v:=v^.next;
   end;
 if v=nil then begin new(v); v^.nod:=y; v^.c:=1; v^.next:=g[x]; g[x]:=v; end;
end;
procedure dfs(nod,prec:longint);
 var p,v:lista;
begin
 p:=g[nod]; if nr<m then write(fo,nod,' ');
 v:=g[nod]; while v<>nil do begin if v^.nod=prec then begin dec(v^.c); break; end; v:=v^.next; end;
 while p<>nil do begin
  if p^.c>0 then begin dec(p^.c); inc(nr); dfs(p^.nod,nod); end;
   p:=p^.next;
  end;
end;
begin
 assign(fi,'ciclueuler.in');
  assign(fo,'ciclueuler.out');
 settextbuf(fi,b1); settextbuf(fo,b2);\
 reset(fi); rewrite(fo);
 readln(fi,n,m);   ok:=true;
  for i:=1 to m do begin
                   readln(fi,x,y);
  if x<>y then begin
                introdu(x,y);
                 introdu(y,x);
                inc(b[x]); inc(b[y]);
                   end
                else begin inc(nr); aux[nr]:=x; end;
              end;
  for i:=1 to nr do begin introdu(aux[nr],aux[nr]); b[aux[nr]]:=b[aux[nr]]+2; end;
   nr:=0;
  for i:=1 to n do
   if b[i] mod 2=1 then ok:=false;
  if ok then dfs(1,0) else write(fo,'-1');
 close(fo);
end.