#![allow(non_snake_case, unused_imports)]
use proconio::{fastout, input, marker::*};

#[fastout]
fn main() {
    input! {
        A:  isize, B: isize,
    }

    let mut r = A % B;
    if r < 0 {
        r += B.abs();
    }

    println!("{}", r);
}