import java.util.*;

public class Main {
    public static void main(String args[]){
        Scanner scanner = new Scanner(System.in);
        long N = scanner.nextLong();
        long K = scanner.nextLong();
        if( N < K ){
            long mi = Math.min(N, K-N);
            System.out.println(mi);
            return;
        }
        if(N % K == 0){
            System.out.println(0);
            return;
        }
        N = N % K;
        System.out.println(Math.min(N, K-N));
        // while(K != 0){
        //     N = N % K;
        //     long temp = N;
        //     N = K;
        //     K = temp;
        // }
        // System.out.println(N);
    }
}
/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