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 Python (3.4.3) (judge verdict: Wrong Answer)

a, b, x = map(int, input().split())

# print(a)
# print(b)
# print(x)

# count = 0
# for i in range(a, b + 1):
#     # print(i)
    
#     if i % x == 0:
#         count += 1
        
# print(count)

def f(n):
    if n == -1:
        return 0
    else:
        return int(n / x) + 1

# print(int((a -1) / x) + 1)
# print(int(b / x))

print(f(b) - f(a - 1))