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)

from heapq import heappush, heappop
from itertools import permutations, accumulate, combinations
import math
import bisect
import numpy as np
from collections import defaultdict, deque
from operator import itemgetter
from bisect import bisect_left, bisect_right
import sys
input = sys.stdin.readline
# sys.setrecursionlimit(10 ** 6)
# MOD = 10 ** 9 + 7
# INF = float("inf")


def main():
    x = int(input())
    a = int(input())
    ans = x -a
    b = int(input())
    ans = ans - (ans // b) * b
    print(ans)

if __name__ == '__main__':
    main()