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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _20200719AtCorder
{
    class Class1
    {
        static void Main(string[] args)
        {
            var possession = int.Parse(Console.ReadLine());
            var cakeprice = int.Parse(Console.ReadLine());
            var donutprice = int.Parse(Console.ReadLine());
            //var afterpayingforcake = possession - cakeprice;
            var numberofdonutsyoucanbuy = (possession - cakeprice) / donutprice;
            var ans = (possession - cakeprice) - donutprice * numberofdonutsyoucanbuy;
            Console.WriteLine(ans);
            Console.ReadLine();
        }
    }
}