import java.util.Scanner;

class Main{

	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		long N = sc.nextLong();
		long K = sc.nextLong();

		long ans = 0;

		if(N>K){
			long x = N / K;
			long ans1 = N - (K * x);
			long ans2 = ((x + 1) * K) - N;
			ans = (ans1 > ans2)? ans2 : ans1;
		}else if(N<K){
			long ans1 = K - N;
			long ans2 = N;
			ans = (ans1 > ans2)? ans2 : ans1;
		}else{
			ans = 0;
		}

		System.out.println(ans);
		// System.out.println(S.toString());

	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz