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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function main(input) 
{
    input = input.split("\n").map(Number);
    var count = 0

    for (i = 0; i < input[0] + 1; i++)
    {
        for (j = 0; j < input[1] + 1; j++)
        {
            for (k = 0; k < input[2] + 1; k++)
            {
                if ((500*i+100*j+50*k) == input[3])
                {
                    count++;
                }
            }
        }
    }
    console.log(count);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));