#include <coding.h>

unsigned char encode(unsigned char c) {
  if ((c >= 'A' && c <= 'Z'))
    return ((c - 'A' + 13) % 26) + 'A';
  else if ((c >= 'a' && c <= 'z'))
    return ((c - 'a' + 13) % 26) + 'a';
  else
    return c; // Non-alphabetic characters are unchanged
}

unsigned char decode(unsigned char c) {
  return encode(c); // ROT13 encoding and decoding are the same
}