import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] lo = reader.readLine().split(" ");
        long N = Long.parseLong(lo[0]);
        long K = Long.parseLong(lo[1]);
        if(N<K){
            System.out.println(Math.min(N,Math.abs(N-K)));
        }
        else if(N>K){
            long q = N/K -1;
            N = N - q*K;
            N = Math.abs(N-K);
            System.out.println(Math.min(N,Math.abs(N-K)));
        }
        else System.out.println(0);
    }
}

/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