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 Ruby (2.3.3) (judge verdict: Accepted)

# 情報を取得
input = gets.chomp.split
a = input[0].to_i
b = input[1].to_i
x = input[2].to_i

puts (b / x) - ((a - 1) / x)

# # x で割り切れるものの個数を格納する変数を宣言
# count = 0

# # a 以上 b 以下の整数において、x で割り切れるか判定
# (a..b).each do |num|
#   if num % x == 0
#     count += 1
#   end
#   num += num
# end

# # 結果を出力
# puts count