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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::*;
use std::str::*;


// while let Some(x)=read(cin) { ... }
fn read<T: FromStr>(s: &mut StdinLock) -> Option<T> {
    let s = s.by_ref().bytes().map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect::<String>();
    s.parse::<T>().ok()
}


fn read_to_vec<T :FromStr>(s: &mut StdinLock) -> Vec<T> {
    let mut v : Vec<T> =Vec::new();
    while let Some(x) = {let d = s.by_ref().bytes().map(|c| c.unwrap() as char)
                         .skip_while(|c| c.is_whitespace())
                         .take_while(|c| !c.is_whitespace())
                         .collect::<String>();
                         d.parse::<T>().ok()} {
        v.push(x);
    }
    v
}


fn main(){
    let cin = stdin();
    let mut cin = cin.lock();
    let cin = &mut cin;
    
    let x:i32 = read(cin).unwrap();
    let a:i32 = read(cin).unwrap();
    let b:i32 =read(cin).unwrap();
    println!("{}",(x-a)%b);

    
}