; alchemical reduction
 
(define (chem str)
  (let loop ((cs (string->list str)) (zs (list)))
    (cond ((null? cs) (reverse zs))
          ((null? zs) (loop (cdr cs) (cons (car cs) zs)))
          ((and (char-ci=? (car cs) (car zs))
                (not (char=? (car cs) (car zs))))
            (loop (cdr cs) (cdr zs)))
          (else (loop (cdr cs) (cons (car cs) zs))))))
 
(do ((str (read) (read))) ((eof-object? str))
  (display (length (chem str))) (newline))

OyBhbGNoZW1pY2FsIHJlZHVjdGlvbgoKKGRlZmluZSAoY2hlbSBzdHIpCiAgKGxldCBsb29wICgoY3MgKHN0cmluZy0+bGlzdCBzdHIpKSAoenMgKGxpc3QpKSkKICAgIChjb25kICgobnVsbD8gY3MpIChyZXZlcnNlIHpzKSkKICAgICAgICAgICgobnVsbD8genMpIChsb29wIChjZHIgY3MpIChjb25zIChjYXIgY3MpIHpzKSkpCiAgICAgICAgICAoKGFuZCAoY2hhci1jaT0/IChjYXIgY3MpIChjYXIgenMpKQogICAgICAgICAgICAgICAgKG5vdCAoY2hhcj0/IChjYXIgY3MpIChjYXIgenMpKSkpCiAgICAgICAgICAgIChsb29wIChjZHIgY3MpIChjZHIgenMpKSkKICAgICAgICAgIChlbHNlIChsb29wIChjZHIgY3MpIChjb25zIChjYXIgY3MpIHpzKSkpKSkpCgooZG8gKChzdHIgKHJlYWQpIChyZWFkKSkpICgoZW9mLW9iamVjdD8gc3RyKSkKICAoZGlzcGxheSAobGVuZ3RoIChjaGVtIHN0cikpKSAobmV3bGluZSkp

JnF1b3Q7QWFiY2RaWnFRJnF1b3Q7CiZxdW90O2FBYnhYQmN0VEN6JnF1b3Q7

"AabcdZZqQ"
"aAbxXBctTCz"