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 min = 0;
    
    if (n > k){
      long a = n%k;
      if (a > 0){
        min = Math.abs(a-k);
      }
    } else if (n < k){
      long a = k-n;
      if (n < a){
        min = n;
      } else {
        min = a;
      }
    }
    
    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