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 Python (3.4.3) (judge verdict: Accepted)

# n=int(input())
# a,b=map(int, input().split())
# c=list(map(int, input().split()))
# s=[list(map(int,list(input()))) for i in range(h)]  # 二次元配列入力　二次元マップみたいな入力のとき

# a=100
# b=0.987654321
# print('{0:06d}-{1:6f}'.format(a,b))  # 0埋めのときの出力
# 000100-0.987654

import numpy as np
import math
import copy

X=int(input())
A=int(input())
B=int(input())

X = X - A
print(X%B)