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)

"use strict";
// import bigInt from 'big-integer'

const Main = input => {
  input = input.trim().split("\n");
  const num500 = input[0];
  const num100 = input[1];
  const num50 = input[2];
  const target = parseInt(input[3], 10);

  const tries = [];
  let count = 0;

  // 500
  for (let i = 0; i < num500; i++) {
    if (target === (i + 1) * 500) count++;
  }
  // 500, 100
  for (let i = 0; i < num500; i++) {
    for (let j = 0; j < num100; j++) {
      if (target === (i + 1) * 500 + (j + 1) * 100) count++;
    }
  }
  // 500, 100, 50
  for (let i = 0; i < num500; i++) {
    for (let j = 0; j < num100; j++) {
      for (let k = 0; k < num50; k++) {
        if (target === (i + 1) * 500 + (j + 1) * 100 + (k + 1) * 50) count++;
      }
    }
  }
  // 500, 50
  for (let i = 0; i < num500; i++) {
    for (let j = 0; j < num50; j++) {
      if (target === (i + 1) * 500 + (j + 1) * 50) count++;
    }
  }
  // 100
  for (let i = 0; i < num100; i++) {
    if (target === (i + 1) * 100) count++;
  }
  // 100, 50
  for (let i = 0; i < num100; i++) {
    for (let j = 0; j < num50; j++) {
      if (target === (i + 1) * 100 + (j + 1) * 50) count++;
    }
  }
  // 50
  for (let i = 0; i < num50; i++) {
    if (target === (i + 1) * 50) count++;
  }

  console.log(count);
};

Main(require("fs").readFileSync("/dev/stdin", "utf8"));