B - Between a and b ... /

### 制約

• 0 ≤ a ≤ b ≤ 10^{18}
• 1 ≤ x ≤ 10^{18}

### 入力

a b x


### 出力

a 以上 b 以下の整数のうち、x で割り切れるものの個数を出力せよ。

### 入力例 1

4 8 2


### 出力例 1

3


4 以上 8 以下の整数のうち 2 で割り切れるものは、4, 6, 8 です。

### 入力例 2

0 5 1


### 出力例 2

6


0 以上 5 以下の整数のうち 1 で割り切れるものは、0, 1, 2, 3, 4, 5 です。

### 入力例 3

9 9 2


### 出力例 3

0


9 以上 9 以下の整数のうち 2 で割り切れるものはありません。

### 入力例 4

1 1000000000000000000 3


### 出力例 4

333333333333333333


オーバーフローに注意してください。

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.