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 PHP (5.6.30) (judge verdict: Wrong Answer)

<?


$input = readline();

$parts = explode(" ", $input);

$low = $parts[0];
$high = $parts[1];

$div = $parts[2];


//first find the lowest

$low_div = $low % $div;
if ($low_div == 0)
{
	$low_min = $low;
}
else
{
	$low_min = $low + ($div - $low_div);
}


//then find the highest
$high_div = $high % $div;
$high_max = $high - $high_div;


//then see how many are in between
$result = ( $high_max - $low_min ) / $div + 1;

echo $result ."\n";