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 (3.8.2) (judge verdict: Accepted)

def generator(x, a): # xの倍数でaより大きいもののうちの最小値
    if x >= a:
        y = x
    else:
        tmp = a // x + 1
        if a % x == 0:
            tmp -= 1
        y = x * tmp

    return y


def main():
    a, b, x = map(int, input().split())
    minimum = generator(x, a)

    if minimum > b:
        count = 0
    else:
        count = (b - minimum) // x + 1

    if a == 0:
        count += 1

    print(count)


if __name__ == '__main__':
    main()