Problem:
Score : 100 points

Problem Statement

You went shopping to buy cakes and donuts with X yen (the currency of Japan).

First, you bought one cake for A yen at a cake shop.
Then, you bought as many donuts as possible for B yen each, at a donut shop.

How much do you have left after shopping?

Constraints

1 \leq A, B \leq 1 000

A + B \leq X \leq 10 000

X, A and B are integers.

Input

Input is given from Standard Input in the following format:

X
A
B

Output

Print the amount you have left after shopping.

Sample Input 1

1234
150
100

Sample Output 1

84

You have 1234 - 150 = 1084 yen left after buying a cake.
With this amount, you can buy 10 donuts, after which you have 84 yen left.

Sample Input 2

1000
108
108

Sample Output 2

28

Sample Input 3

579
123
456

Sample Output 3

0

Sample Input 4

7477
549
593

Sample Output 4

405

Solution in PHP (5.6.30) (judge verdict: Wrong Answer)

<?php
$step = trim(fgets(STDIN));
$rows = [];

while (($row = trim(fgets(STDIN))) !== '') {
  $rows[] = explode(' ', $row);
}

$memo = [];

for ($i=0; $i < $step; $i++) {
  $result = 0;
  for ($j=0; $j <= $i; $j++) {
    $result += $rows[0][$j];
  }
  for ($j=$i; $j < $step; $j++) {
    $result += $rows[1][$j];
  }
  $memo[] = $result;
}

echo max($memo)."\n";