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 = new long [2];
      long div = 0;
      div = n / k;
      a[0] = k * div;
      a[1] = k * (div+1);

      long min = n;
      if( n - a[0] >= 0 && n - a[0] < min ){
        min = n - a[0];
      }
      if( a[1] - n >= 0 && a[1] - n < min ){
        min = a[1] - n;
      }
      System.out.println(min);
	}
}
/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