(let* ((char "0123456789abcdefghijklnmopqrstuvwxyzABCDEFGHIJKLNMOPQRSTUVWXYZ")
(radix (length char)))
(defun radix62 (n &optional (ret nil))
(if (zerop n)
(concatenate 'string ret)
(radix62 (floor n radix) (cons (elt char (mod n radix)) ret)))))
(let ((n 18446744073709551615))
(format t "~d==~a~%" n (radix62 n)))
KGxldCogKChjaGFyICIwMTIzNDU2Nzg5YWJjZGVmZ2hpamtsbm1vcHFyc3R1dnd4eXpBQkNERUZHSElKS0xOTU9QUVJTVFVWV1hZWiIpCiAgICAgICAocmFkaXggKGxlbmd0aCBjaGFyKSkpCiAgKGRlZnVuIHJhZGl4NjIgKG4gJm9wdGlvbmFsIChyZXQgbmlsKSkKICAgIChpZiAoemVyb3AgbikKCQkoY29uY2F0ZW5hdGUgJ3N0cmluZyByZXQpCgkJKHJhZGl4NjIgKGZsb29yIG4gcmFkaXgpIChjb25zIChlbHQgY2hhciAobW9kIG4gcmFkaXgpKSByZXQpKSkpKQoKKGxldCAoKG4gMTg0NDY3NDQwNzM3MDk1NTE2MTUpKQogIChmb3JtYXQgdCAifmQ9PX5hfiUiIG4gKHJhZGl4NjIgbikpKQ==