import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.util.Set;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.LinkedHashSet;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author L_aka_ryuga
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        CReplacingInteger solver = new CReplacingInteger();
        solver.solve(1, in, out);
        out.close();
    }

    static class CReplacingInteger {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void println(long i) {
            writer.println(i);
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
}
 import java.io.OutputStream; OutputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.OutputStream; OutputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.io.BufferedWriter; BufferedWriter java.io import java.io.Writer; Writer java.io import java.util.Set; Set java.util import java.io.OutputStreamWriter; OutputStreamWriter java.io import java.util.InputMismatchException; InputMismatchException java.util import java.io.IOException; IOException java.io import java.util.LinkedHashSet; LinkedHashSet java.util import java.io.InputStream; InputStream java.io public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        CReplacingInteger solver = new CReplacingInteger();
        solver.solve(1, in, out);
        out.close();
    }

    static class CReplacingInteger {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void println(long i) {
            writer.println(i);
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        CReplacingInteger solver = new CReplacingInteger();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        CReplacingInteger solver = new CReplacingInteger();
        solver.solve(1, in, out);
        out.close();
    } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out InputReader in = new InputReader(inputStream); in new InputReader(inputStream) OutputWriter out = new OutputWriter(outputStream); out new OutputWriter(outputStream) CReplacingInteger solver = new CReplacingInteger(); solver new CReplacingInteger() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class CReplacingInteger {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        }

    } CReplacingInteger public void solve(int testNumber, InputReader in, OutputWriter out) {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        } solve {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        } long n1 = in.nl() n1 in.nl() in.nl in k1 = in.nl(); k1 in.nl() in.nl in long ans = 0; ans 0 if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            } n1 == k1 n1 k1 {
                ans = 0;
            } ans = 0 ans 0 if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            } n1 < k1 n1 k1 {
                ans = Math.min(n1, k1 - n1);
            } ans = Math.min(n1, k1 - n1) ans Math.min(n1, k1 - n1) Math.min Math n1 k1 - n1 k1 n1 {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            } n1 = n1 - k1 * (n1 / k1) n1 n1 - k1 * (n1 / k1) n1 k1 * (n1 / k1) k1 (n1 / k1) n1 k1 long min1 = Long.MAX_VALUE; min1 Long.MAX_VALUE Long Long.MAX_VALUE Set<Long> set1 = new LinkedHashSet<>(); set1 new LinkedHashSet<>() while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                } true {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                } if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    } n1 % k1 == 0 n1 % k1 n1 k1 0 {
                        min1 = 0;
                        break;
                    } min1 = 0 min1 0 break; n1 = Math.abs(n1 - k1) n1 Math.abs(n1 - k1) Math.abs Math n1 - k1 n1 k1 min1 = Math.min(min1, n1) min1 Math.min(min1, n1) Math.min Math min1 n1 if (!set1.contains(min1)) set1.add(min1);
                    else break; !set1.contains(min1) set1.contains(min1) set1.contains set1 min1 set1.add(min1) set1.add set1 min1 break; ans = min1 ans min1 out.println(ans) out.println out ans int testNumber testNumber InputReader in in OutputWriter out out static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void println(long i) {
            writer.println(i);
        }

    } OutputWriter private final PrintWriter writer; writer public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        } OutputWriter {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        } writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream))) writer new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream))) OutputStream outputStream outputStream public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        } OutputWriter {
            this.writer = new PrintWriter(writer);
        } this.writer = new PrintWriter(writer) this.writer this this.writer new PrintWriter(writer) Writer writer writer public void close() {
            writer.close();
        } close {
            writer.close();
        } writer.close() writer.close writer public void println(long i) {
            writer.println(i);
        } println {
            writer.println(i);
        } writer.println(i) writer.println writer i long i i static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    } InputReader private InputStream stream; stream private byte[] buf = new byte[1024]; buf new byte[1024] 1024 private int curChar; curChar private int numChars; numChars private InputReader.SpaceCharFilter filter; filter public InputReader(InputStream stream) {
            this.stream = stream;
        } InputReader {
            this.stream = stream;
        } this.stream = stream this.stream this this.stream stream InputStream stream stream public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        } read {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        } if (numChars == -1) {
                throw new InputMismatchException();
            } numChars == -1 numChars -1 1 {
                throw new InputMismatchException();
            } throw new InputMismatchException(); new InputMismatchException() if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            } curChar >= numChars curChar numChars {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            } curChar = 0 curChar 0 try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                } catch (IOException e) {
                    throw new InputMismatchException();
                } IOException e {
                    throw new InputMismatchException();
                } throw new InputMismatchException(); new InputMismatchException() {
                    numChars = stream.read(buf);
                } numChars = stream.read(buf) numChars stream.read(buf) stream.read stream buf if (numChars <= 0) {
                    return -1;
                } numChars <= 0 numChars 0 {
                    return -1;
                } return -1; -1 1 return buf[curChar++]; buf[curChar++] buf curChar++ curChar public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } nl {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } int c = read(); c read() read while (isSpaceChar(c)) {
                c = read();
            } isSpaceChar(c) isSpaceChar c {
                c = read();
            } c = read() c read() read int sgn = 1; sgn 1 if (c == '-') {
                sgn = -1;
                c = read();
            } c == '-' c '-' {
                sgn = -1;
                c = read();
            } sgn = -1 sgn -1 1 c = read() c read() read long res = 0; res 0 do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                } c < '0' || c > '9' c < '0' c '0' c > '9' c '9' {
                    throw new InputMismatchException();
                } throw new InputMismatchException(); new InputMismatchException() res *= 10 res 10 res += c - '0' res c - '0' c '0' c = read() c read() read return res * sgn; res * sgn res sgn public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        } isSpaceChar {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        } if (filter != null) {
                return filter.isSpaceChar(c);
            } filter != null filter null {
                return filter.isSpaceChar(c);
            } return filter.isSpaceChar(c); filter.isSpaceChar(c) filter.isSpaceChar filter c return isWhitespace(c); isWhitespace(c) isWhitespace c int c c public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        } isWhitespace {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        } return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == '\t' c == '\r' c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == ' ' c ' ' c == '\n' c '\n' c == '\r' c '\r' c == '\t' c '\t' c == -1 c -1 1 int c c public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        } SpaceCharFilter public boolean isSpaceChar(int ch); isSpaceChar int ch ch public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        CReplacingInteger solver = new CReplacingInteger();
        solver.solve(1, in, out);
        out.close();
    }

    static class CReplacingInteger {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void println(long i) {
            writer.println(i);
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
} public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        CReplacingInteger solver = new CReplacingInteger();
        solver.solve(1, in, out);
        out.close();
    }

    static class CReplacingInteger {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void println(long i) {
            writer.println(i);
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.util.Set;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.LinkedHashSet;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author L_aka_ryuga
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        CReplacingInteger solver = new CReplacingInteger();
        solver.solve(1, in, out);
        out.close();
    }

    static class CReplacingInteger {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
/*
        for(int i = 0; i <= 100;i++){
            for(int j = 1;j <= 100 ;j++)
            {

            long n = in.nl() , k = in.nl();
                long min = Long.MAX_VALUE;
                Set<Long> set = new LinkedHashSet<>();

                for(long i = 0 ; i <= Long.MAX_VALUE - 1     ; i++){
                    if(n%k == 0){
                        min = 0;
                        break;
                    }
                    n = Math.abs(n - k);
                    min = Math.min(min , n);
                    /*if(!set.contains(min)) set.add(min);
                    else break;

                }

                out.println(min);
        */
            long n1 = in.nl(), k1 = in.nl();
            long ans = 0;
            if (n1 == k1) {
                ans = 0;
            } else if (n1 < k1) {
                ans = Math.min(n1, k1 - n1);
            } else {
                n1 = n1 - k1 * (n1 / k1);
                long min1 = Long.MAX_VALUE;
                Set<Long> set1 = new LinkedHashSet<>();
                while (true) {
                    if (n1 % k1 == 0) {
                        min1 = 0;
                        break;
                    }
                    n1 = Math.abs(n1 - k1);
                    min1 = Math.min(min1, n1);
                    if (!set1.contains(min1)) set1.add(min1);
                    else break;

                }
                ans = min1;
            }

            out.println(ans);


        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void println(long i) {
            writer.println(i);
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
}

