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();
    if(N < K){
      long A = K -N;
      if(A >= N){
        System.out.println(N); 
      }else{
        System.out.println(A); 
      }
    }else{
      long B = N % K;
      long A = K - B;
      if(A >= B){
        System.out.println(B); 
      }else{
        System.out.println(A); 
      }
    }
    return;
  }
}


/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