$ include "seed7_05.s7i";

const proc: main is func
  local
    var char: ch is ' ';
  begin
    ch := getc(IN);
    while not eof(IN) do
      if (ch >= 'a' and ch <= 'm') or (ch >= 'A' and ch <= 'M') then
        ch := chr(ord(ch) + 13);
      elsif (ch >= 'n' and ch <= 'z') or (ch >= 'N' and ch <= 'Z') then
        ch := chr(ord(ch) - 13);
      end if;
      write(ch);
      ch := getc(IN);
    end while;
  end func;