import java.util.*;
import java.lang.*;
public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long N = sc.nextLong();
		long K = sc.nextLong();
		long A = N%K;
		long ans = 0;
		if( N<K ){
			long a = K-N;
			ans = Math.min( a,N );
		}
		if( N%K==0 ){
			ans = 0;
		}
		if( !(N<K) && !(N%K==0) ){
			long a = A;
			long b = K-A;
			if( a<b ){
				ans = a;
			}else{
				ans = b;
			}
		}
		System.out.println(ans);
	}
}

/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