program ciclueuler;

type pnod=^nod;
     nod=record inf,nro:integer; urm:pnod; end;

var fi,fo:Text;
    bufin,bufout:array[1..1 shl 17]of char;
    m,n,ind,i:integer;
    l:array[1..100000]of pnod;
    scos:Array[1..10000,1..10000]of integer;
    trecut:array[1..100000]of 0..1;
    sol:array[1..100000]of integer;

    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;
    end;

  procedure citire;
  var i,x,y:integer;
  begin
      readln(fi,n,m);
      for i:=1 to m do
        begin
            readln(fi,x,y);
            inc(scos[x,y]);
            inc(scos[y,x]);
            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 scos[nod,p^.inf]>0 then
              begin
                  dec(scos[nod,p^.inf]);
                  dec(scos[p^.inf,nod]);
                  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;

      for i:=1 to n do
        if trecut[i]=0 then
          euler(i);

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

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