(define c (string->list (read-line)))
(define ca (char->integer #\A))
(define (dec c i a)
        (if (null? c) (reverse a)
                      (dec (cdr c)
                          (+ i 1)
                          (cons (integer->char
                                  (+ (modulo (- (- (char->integer (car c)) ca) i)
                                              26)
                                      ca))
                                a))))
(print (list->string(dec c 1 '())))