#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>

/* This macro gives the maximum key size. */

#define MAX_KEY_SIZE 10

/* This global variable stores the offsets given by the key */

int key[MAX_KEY_SIZE];

/* This global variable stores the size of the key in use */

int keysize = 0;

/* This function, to be completed by the candidate, gets the key
   from the input and stores it in key and keysize
   The function should read characters from the input until a newline
   character, and turn those characters into a key as specified in the
   question.
   It should read but ignore any key characters after it has processed
   MAX_KEY_SIZE key letters.
*/

void ReadKey() {
  /* BEGIN SOLUTION (a) */

  /* END SOLUTION (a) */
}

/* This function, to be completed by the candidate, en/deciphers a single
   letter according to the key. Arguments:
   char c : the letter to be en/deciphered. Should be an uppercase letter.
   int decipher : true (1) if the letter is to be deciphered,
                  false (0) if the letter is to be enciphered
   int count : the number of letters that have already been ciphered
   Return value: the ciphered letter.
*/
char cipher(char c, int decipher, int count) {
  /* check the input letter is valid */
  if ( ! isalpha(c) || ! isupper(c) ) {
    fprintf(stderr,"cipher() called on non-(uppercase letter) %c\n",c);
    exit(-1);
  }
  /* BEGIN SOLUTION (b) */

  /* END SOLUTION (b) */
}

int main(int argc, char *argv[]) {
  int decipher = 0;
  int c;
  int count = 0;
  if ( argc > 1 && strcmp(argv[1],"-d") == 0 ) {
    decipher = 1;
  }
  ReadKey();

  while ( (c = getchar()) != EOF ) {
    if ( isalpha(c) ) {
      putchar(cipher(toupper(c),decipher,count));
      count++;
    } else {
      putchar(c);
    }
  }
  return EXIT_SUCCESS;
}