program ciclueuler;

type pnod=^nod;
     nod=record inf,nro:integer; urm:pnod; end;
     muchie=record ns,nd,cate:integer; end;

var fi,fo:Text;
    //bufin,bufout:array[1..1 shl 17]of char;
    m,n,ind,i,nrm,unde,eulerian:integer;
    l:array[1..100000]of pnod;
    trecut,viz:array[1..100000]of 0..1;
    sol:array[1..100000]of integer;
    muchii:array[1..100000]of muchie;

    procedure push_back(nod,vecin,muchie:integer);
    var p:pnod;
    begin
        new(p); p^.inf:=vecin; p^.nro:=muchie; p^.urm:=l[nod]; l[nod]:=p;
        inc(sol[nod]); inc(sol[vecin]);
    end;

  procedure citire;
  var i,x,y:integer;
  begin
      readln(fi,n,m);
      for i:=1 to m do
        begin
            readln(fi,x,y);
            push_back(x,y,i);
            push_back(y,x,i);
        end;
  end;

  procedure euler(nod:integer);
  var p:pnod;
  begin
      trecut[nod]:=1;
      p:=l[nod];
      while p<>nil do
        begin
            if viz[p^.nro]=0 then
              begin
                  viz[p^.nro]:=1;
                  euler(p^.inf);
              end;
            p:=p^.urm;
        end;
      inc(ind);
      sol[ind]:=nod;
  end;

begin
    assign(fi,'ciclueuler.in'); reset(fi); //settextbuf(fi,bufin);
    assign(fo,'ciclueuler.out'); rewrite(fo); //settextbuf(fo,bufout);

      citire;

      eulerian:=1;

      //verific daca e eulerian
      for i:=1 to n do
        if sol[i] mod 2=1 then
          begin
              eulerian:=0;
              break;
          end;

      if eulerian=1 then
        begin

          for i:=1 to n do
            if trecut[i]=0 then
              euler(i);
        end
      else
        writeln(fo,-1);

      for i:=1 to ind-1 do
        write(fo,sol[i],' ');

    close(fi); close(fo);
end.