(define (main)
  (let ((input (read-line)))
    (display (count-tree input))
    (newline)))

(define (count-tree str)
  (let ((char-list (string->list str))
        (count-char-lambdas (list (count-char #\t)
                                  (count-char #\r)
                                  (div2 (count-char #\e)))))
    (define (apply-lambdas lst arg)
      (if (equal? '() lst)
          lst
          (cons ((car lst) arg) (apply-lambdas (cdr lst) arg))))
    (minimum (apply-lambdas count-char-lambdas char-list))))

(define (minimum lst)
  (define (iter lst holder)
    (if (null? lst)
        holder
        (if (< holder (car lst))
            (iter (cdr lst) holder)
            (iter (cdr lst) (car lst)))))
  (iter (cdr lst) (car lst)))

(define (div2 f)
  (lambda (x)
    (/ (f x) 2)))

(define (count-char char)
  (lambda (x)
    (define (iter x i)
      (if (equal? x '())
          i
          (if (equal? (car x) char)
              (iter (cdr x) (+ i 1))
              (iter (cdr x) i))))
    (iter x 0)))
(main)