with TEXT_IO; use TEXT_IO;
procedure ROT13 is
    foo : CHARACTER;
begin
    while not END_OF_FILE(STANDARD_INPUT) loop
      GET(foo);
      if (foo >= 'a' and foo <= 'm') or (foo >= 'A' and foo <= 'M') then
        foo:=CHARACTER'VAL(CHARACTER'POS(foo)+13);
      elsif (foo >= 'n' and foo <= 'z') or (foo >= 'N' and foo <= 'Z') then
        foo:=CHARACTER'VAL(CHARACTER'POS(foo)-13);
      end if;
      PUT(foo);
    end loop;
    NEW_LINE;
end;