import java.util.*;
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==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		}
		System.out.println(ans);
	}
} import java.util.*; util.* java 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==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		}
		System.out.println(ans);
	}
} 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==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		}
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);

		long N = sc.nextLong();
		long K = sc.nextLong();
		long A = N%K;
		long ans = 0;
		if( N%K==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		}
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long N = sc.nextLong(); N sc.nextLong() sc.nextLong sc long K = sc.nextLong(); K sc.nextLong() sc.nextLong sc long A = N%K; A N%K N K long ans = 0; ans 0 if( N%K==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		} N%K==0 N%K N K 0 {
			ans = 0;
		} ans = 0 ans 0 {
			ans = Math.min( A,K-A );
		} ans = Math.min( A,K-A ) ans Math.min( A,K-A ) Math.min Math A K-A K A System.out.println(ans) System.out.println System.out System System.out ans String[] args args 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==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		}
		System.out.println(ans);
	}
} 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==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		}
		System.out.println(ans);
	}
} Main
import java.util.*;
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==0 ){
			ans = 0;
		}else{
			ans = Math.min( A,K-A );
		}
		System.out.println(ans);
	}
}
