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 Ruby (2.3.3) (judge verdict: Runtime Error)

n=gets.chomp.to_i
fst=gets.chomp.split(" ").map{|str| str.to_i}
snd=gets.chomp.split(" ").map{|str| str.to_i}

max=0

n.times do |i|
  total=0
  (0..i).each do |j|
    total+=fst[j]
  end
  (i..n-1).each do |j|
    total+=snd[j]
  end

  if total>max then
    max=total
  end

end
puts max