while pos('//', mystr) <> 0 do
 delete(mystr, pos('//', mystr), 2)

Program DeleteOfficialSymbols;
Uses
   Crt;
Const
    S:String = 'affffb&&&cdefg  ..//hheudsloi--((**jksla8ew%%';
Var
  l:Byte;
Begin
    ClrScr;
    Randomize;
    For l:=2 to Length(S)-1 do
    If (S[l]=S[l+1]) or (S[l-1]=S[l]) then
    Case Ord(S[l]) of
    1..47,58..64,91..96,123..127,176..223,240..254:S[l]:=#255;
    end;
    While Pos(#255,S)<>0 do Delete(S,Pos(#255,S),1);
    WriteLn(S);
End.