t_17_11_v1_volkovich

procedure copy(T:tree);
begin
    if T<>nil then
         begin
            new(T^);
            T^^.elem:=T^.elem;
            copy(T^.left,T^^.left);
            copy(T^.right,T^^.right);
            {T^^.right:=nil;
            T^^.left:=nil;}
         end;
    T^:=nil;
end;