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 Perl (v5.18.2) (judge verdict: Wrong Answer)

#!/usr/bin/perl

$c500 = <STDIN>;
$c100 = <STDIN>;
$c50 = <STDIN>;
$amount = <STDIN>;
$count = 0;

for ($i = 0; $i <= $c500; $i++) {
        if ($i * 500 > $amount) {
                last;
        }
        for ($j = 0; $j <= $c100; $j++) {
                if ($i * 500 + $j * 100 > $amount) {
                        last;
                }
                if ($i * 500 + $j * 100 + $c50 * 50 < $amount) {
                        last;
                }
                for ($k = 0; $k <= $c50; $k++) {
                        if ($i * 500 + $j * 100 + $k * 50 == $amount) {
                                $count++;
                                last;
                        }
                }
        }
}

print "$count\n";