import java.util.*;
import java.io.*;
import java.lang.*;
class Main {
    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;

        public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt()
        {
            return Integer.parseInt(next());
        }

        long nextLong()
        {
            return Long.parseLong(next());
        }

        double nextDouble()
        {
            return Double.parseDouble(next());
        }

        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
    public static void main(String[] args) {
        FastReader ob = new FastReader();
        long n = ob.nextLong(),k=ob.nextLong();
        if(k>n){
            System.out.println(Math.min(k-n,n));
        }
        else{
            System.out.println(Math.min(n%k,k-(n%k)));
        }



    }
} import java.util.*; util.* java import java.io.*; io.* java import java.lang.*; lang.* java class Main {
    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;

        public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt()
        {
            return Integer.parseInt(next());
        }

        long nextLong()
        {
            return Long.parseLong(next());
        }

        double nextDouble()
        {
            return Double.parseDouble(next());
        }

        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
    public static void main(String[] args) {
        FastReader ob = new FastReader();
        long n = ob.nextLong(),k=ob.nextLong();
        if(k>n){
            System.out.println(Math.min(k-n,n));
        }
        else{
            System.out.println(Math.min(n%k,k-(n%k)));
        }



    }
} Main public static void main(String[] args) {
        FastReader ob = new FastReader();
        long n = ob.nextLong(),k=ob.nextLong();
        if(k>n){
            System.out.println(Math.min(k-n,n));
        }
        else{
            System.out.println(Math.min(n%k,k-(n%k)));
        }



    } main {
        FastReader ob = new FastReader();
        long n = ob.nextLong(),k=ob.nextLong();
        if(k>n){
            System.out.println(Math.min(k-n,n));
        }
        else{
            System.out.println(Math.min(n%k,k-(n%k)));
        }



    } FastReader ob = new FastReader(); ob new FastReader() long n = ob.nextLong() n ob.nextLong() ob.nextLong ob k=ob.nextLong(); k ob.nextLong() ob.nextLong ob if(k>n){
            System.out.println(Math.min(k-n,n));
        }
        else{
            System.out.println(Math.min(n%k,k-(n%k)));
        } k>n k n {
            System.out.println(Math.min(k-n,n));
        } System.out.println(Math.min(k-n,n)) System.out.println System.out System System.out Math.min(k-n,n) Math.min Math k-n k n n {
            System.out.println(Math.min(n%k,k-(n%k)));
        } System.out.println(Math.min(n%k,k-(n%k))) System.out.println System.out System System.out Math.min(n%k,k-(n%k)) Math.min Math n%k n k k-(n%k) k (n%k) n k String[] args args static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;

        public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt()
        {
            return Integer.parseInt(next());
        }

        long nextLong()
        {
            return Long.parseLong(next());
        }

        double nextDouble()
        {
            return Double.parseDouble(next());
        }

        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    } FastReader BufferedReader br; br StringTokenizer st; st public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        } FastReader {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        } br = new BufferedReader(new
                    InputStreamReader(System.in)) br new BufferedReader(new
                    InputStreamReader(System.in)) String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        } next {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        } while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            } try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                } catch (IOException  e)
                {
                    e.printStackTrace();
                } IOException  e {
                    e.printStackTrace();
                } e.printStackTrace() e.printStackTrace e {
                    st = new StringTokenizer(br.readLine());
                } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt()
        {
            return Integer.parseInt(next());
        } nextInt {
            return Integer.parseInt(next());
        } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nextLong()
        {
            return Long.parseLong(next());
        } nextLong {
            return Long.parseLong(next());
        } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble()
        {
            return Double.parseDouble(next());
        } nextDouble {
            return Double.parseDouble(next());
        } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        } nextLine {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        } String str = ""; str "" try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            } catch (IOException e)
            {
                e.printStackTrace();
            } IOException e {
                e.printStackTrace();
            } e.printStackTrace() e.printStackTrace e {
                str = br.readLine();
            } str = br.readLine() str br.readLine() br.readLine br return str; str
import java.util.*;
import java.io.*;
import java.lang.*;
class Main {
    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;

        public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt()
        {
            return Integer.parseInt(next());
        }

        long nextLong()
        {
            return Long.parseLong(next());
        }

        double nextDouble()
        {
            return Double.parseDouble(next());
        }

        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
    public static void main(String[] args) {
        FastReader ob = new FastReader();
        long n = ob.nextLong(),k=ob.nextLong();
        if(k>n){
            System.out.println(Math.min(k-n,n));
        }
        else{
            System.out.println(Math.min(n%k,k-(n%k)));
        }



    }
}