1157.scm

(define (find-max-char lst)
  (let ((max-value (apply max lst)))
       (do ((lst lst (cdr lst))
            (acc '() acc)
            (n 0 (+ n 1))
            (isambiguses #f isambiguses))
         ((null? lst) (if isambiguses
                        (print "?")
                        (print (integer->char (+ (car acc) (char->integer #\A))))))
         (if (= max-value (car lst))
           (if (null? acc)
               (set! acc (cons n acc))
               (set! isambiguses #t))))))
(let ((alpha-list (make-vector 26 0)))
  (do ((alpha-list alpha-list alpha-list)
       (c (read-char) (read-char)))
    ((eof-object? c) (find-max-char (vector->list alpha-list)))
    (case c
      ((#\a #\A) (vector-set! alpha-list 0 (+ 1 (vector-ref alpha-list 0))))
      ((#\b #\B) (vector-set! alpha-list 1 (+ 1 (vector-ref alpha-list 1))))
      ((#\c #\C) (vector-set! alpha-list 2 (+ 1 (vector-ref alpha-list 2))))
      ((#\d #\D) (vector-set! alpha-list 3 (+ 1 (vector-ref alpha-list 3))))
      ((#\e #\E) (vector-set! alpha-list 4 (+ 1 (vector-ref alpha-list 4))))
      ((#\f #\F) (vector-set! alpha-list 5 (+ 1 (vector-ref alpha-list 5))))
      ((#\g #\G) (vector-set! alpha-list 6 (+ 1 (vector-ref alpha-list 6))))
      ((#\h #\H) (vector-set! alpha-list 7 (+ 1 (vector-ref alpha-list 7))))
      ((#\i #\I) (vector-set! alpha-list 8 (+ 1 (vector-ref alpha-list 8))))
      ((#\j #\J) (vector-set! alpha-list 9 (+ 1 (vector-ref alpha-list 9))))
      ((#\k #\K) (vector-set! alpha-list 10 (+ 1 (vector-ref alpha-list 10))))
      ((#\l #\L) (vector-set! alpha-list 11 (+ 1 (vector-ref alpha-list 11))))
      ((#\m #\M) (vector-set! alpha-list 12 (+ 1 (vector-ref alpha-list 12))))
      ((#\n #\N) (vector-set! alpha-list 13 (+ 1 (vector-ref alpha-list 13))))
      ((#\o #\O) (vector-set! alpha-list 14 (+ 1 (vector-ref alpha-list 14))))
      ((#\p #\P) (vector-set! alpha-list 15 (+ 1 (vector-ref alpha-list 15))))
      ((#\q #\Q) (vector-set! alpha-list 16 (+ 1 (vector-ref alpha-list 16))))
      ((#\r #\R) (vector-set! alpha-list 17 (+ 1 (vector-ref alpha-list 17))))
      ((#\s #\S) (vector-set! alpha-list 18 (+ 1 (vector-ref alpha-list 18))))
      ((#\t #\T) (vector-set! alpha-list 19 (+ 1 (vector-ref alpha-list 19))))
      ((#\u #\U) (vector-set! alpha-list 20 (+ 1 (vector-ref alpha-list 20))))
      ((#\v #\V) (vector-set! alpha-list 21 (+ 1 (vector-ref alpha-list 21))))
      ((#\w #\W) (vector-set! alpha-list 22 (+ 1 (vector-ref alpha-list 22))))
      ((#\x #\X) (vector-set! alpha-list 23 (+ 1 (vector-ref alpha-list 23))))
      ((#\y #\Y) (vector-set! alpha-list 24 (+ 1 (vector-ref alpha-list 24))))
      ((#\z #\Z) (vector-set! alpha-list 25 (+ 1 (vector-ref alpha-list 25)))))))