Problem:
Score : 200 points

Problem Statement

You are given nonnegative integers a and b (a ≤ b), and a positive integer x.
Among the integers between a and b, inclusive, how many are divisible by x?

Constraints

0 ≤ a ≤ b ≤ 10^{18}

1 ≤ x ≤ 10^{18}

Input

The input is given from Standard Input in the following format:

a b x

Output

Print the number of the integers between a and b, inclusive, that are divisible by x.

Sample Input 1

4 8 2

Sample Output 1

3

There are three integers between 4 and 8, inclusive, that are divisible by 2: 4, 6 and 8.

Sample Input 2

0 5 1

Sample Output 2

6

There are six integers between 0 and 5, inclusive, that are divisible by 1: 0, 1, 2, 3, 4 and 5.

Sample Input 3

9 9 2

Sample Output 3

0

There are no integer between 9 and 9, inclusive, that is divisible by 2.

Sample Input 4

1 1000000000000000000 3

Sample Output 4

333333333333333333

Watch out for integer overflows.

Solution in Common Lisp (SBCL 1.1.14) (judge verdict: Time Limit Exceeded)

(defun split (str delim)
  (let ((res (make-array 1 :element-type 'string
                           :fill-pointer 0
                           :adjustable t)))
    (loop for i from 0 below (length str)
          with start = 0
          when (eq (char str i) delim)
          do (vector-push-extend (subseq str start i) res)
             (setf start (1+ i))
          finally (let ((tail (subseq str start)))
                    (when tail
                      (vector-push-extend tail res))))
    res))

(let* ((in (split (read-line) #\Space))
       (a (parse-integer (aref in 0)))
       (b (parse-integer (aref in 1)))
       (x (parse-integer (aref in 2)))
       (cnt 0))
  (loop for i from a upto b
        when (integerp (/ i x))
        do (incf cnt))
  (format t "~A~%" cnt))