Problem:
Score : 100 points

Problem Statement

Snuke has a favorite restaurant.

The price of any meal served at the restaurant is 800 yen (the currency of Japan), and each time a customer orders 15 meals, the restaurant pays 200 yen back to the customer.

So far, Snuke has ordered N meals at the restaurant.
Let the amount of money Snuke has paid to the restaurant be x yen, and let the amount of money the restaurant has paid back to Snuke be y yen.
Find x-y.

Constraints

1 ≤ N ≤ 100

Input

The input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

20

Sample Output 1

15800

So far, Snuke has paid 16000 yen, and the restaurant has paid back 200 yen. Thus, the answer is 15800.

Sample Input 2

60

Sample Output 2

47200

Snuke has paid 48000 yen for 60 meals, and the restaurant has paid back 800 yen.

Solution in PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
$input = trim(fgets(STDIN));
$array = explode(" ",$input);
$s = $array[0];
$c = $array[1];
$scc = 0;

if ( $c <= 1 ) {
  return;
}

$count = floor($c / 2);

for ($i = 1; $i <= $count; $i++) {
  if ( $s === 0 && $c >= 4) {
    $scc += floor($c / 4);
    $c -= floor($c / 4) * 4;
  } else {
    $s = $s - 1;
    $c = $c - 2;
    // echo "s:" . $s . " c:" . $c . "\n";
    if ( $s >= 0 && $c >= 0) {
      $scc += 1;
    }
  }
  
  // echo "scc:" . $scc . "\n";
  if($s === 0 && $c < 4) {
    break;
  } elseif( $c <= 1) {
    break;
  }
}

echo $scc . "\n";