Takahashi is distributing N balls to K persons.

If each person has to receive at least one ball, what is the maximum possible difference in the number of balls received between the person with the most balls and the person with the fewest balls?

Constraints

* 1 \leq K \leq N \leq 100
* All values in input are integers.

Input

Input is given from Standard Input in the following format:


N K


Output

Print the maximum possible difference in the number of balls received.

Examples

Input

3 2


Output

1


Input

3 1


Output

0


Input

8 5


Output

3
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {

    static PrintWriter out;
    static InputReader sc;

    static void solve() {
        int N = sc.nextInt();
        int K = sc.nextInt();
        int[] p = new int[K];
        int idx = 0;
        while (N > 0 && idx < K) {
            idx++;
            p[idx % K]++;
            N--;
        }
        p[0] += N;
        out.println(p[0] - p[K - 1]);
    }

    public static void main(String[] args) {
        sc = new InputReader(System.in);
        out = new PrintWriter(System.out);
        solve();
        out.flush();
    }

    public static class ArraysFillEx {

        public static void fill(Object array, Object value) {

            // 第一引数が配列か判定
            Class<?> type = array.getClass();
            if (!type.isArray()) {
                throw new IllegalArgumentException("not array");
            }

            // クラスの型を判定
            String arrayClassName = array.getClass().getSimpleName().replace("[]", "").toLowerCase();
            String valueClassName = value.getClass().getSimpleName().toLowerCase().replace("character", "char")
                    .replace("integer", "int");
            if (!arrayClassName.equals(valueClassName)) {
                throw new IllegalArgumentException("does not match");
            }

            // 処理
            if (type.getComponentType().isArray()) {
                for (Object o : (Object[]) array) {
                    fill(o, value);
                }
            } else if (array instanceof boolean[]) {
                Arrays.fill((boolean[]) array, (boolean) value);
            } else if (array instanceof char[]) {
                Arrays.fill((char[]) array, (char) value);
            } else if (array instanceof byte[]) {
                Arrays.fill((byte[]) array, (byte) value);
            } else if (array instanceof short[]) {
                Arrays.fill((short[]) array, (short) value);
            } else if (array instanceof int[]) {
                Arrays.fill((int[]) array, (int) value);
            } else if (array instanceof long[]) {
                Arrays.fill((long[]) array, (long) value);
            } else if (array instanceof float[]) {
                Arrays.fill((float[]) array, (float) value);
            } else if (array instanceof double[]) {
                Arrays.fill((double[]) array, (double) value);
            } else {
                Arrays.fill((Object[]) array, value);
            }
        }

    }

    static class InputReader {

        private InputStream in;
        private byte[] buffer = new byte[1024];
        private int curbuf;
        private int lenbuf;

        public InputReader(InputStream in) {
            this.in = in;
            this.curbuf = this.lenbuf = 0;
        }

        public boolean hasNextByte() {
            if (this.curbuf >= this.lenbuf) {
                this.curbuf = 0;
                try {
                    this.lenbuf = this.in.read(this.buffer);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (this.lenbuf <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (this.hasNextByte()) {
                return this.buffer[this.curbuf++];
            } else {
                return -1;
            }
        }

        private boolean isSpaceChar(int c) {
            return !(c >= 33 && c <= 126);
        }

        private void skip() {
            while (this.hasNextByte() && this.isSpaceChar(this.buffer[this.curbuf])) {
                this.curbuf++;
            }
        }

        public boolean hasNext() {
            this.skip();
            return this.hasNextByte();
        }

        public String next() {
            if (!this.hasNext()) {
                throw new NoSuchElementException();
            }
            StringBuilder sb = new StringBuilder();
            int b = this.readByte();
            while (!this.isSpaceChar(b)) {
                sb.appendCodePoint(b);
                b = this.readByte();
            }
            return sb.toString();
        }

        public int nextInt() {
            if (!this.hasNext()) {
                throw new NoSuchElementException();
            }
            int c = this.readByte();
            while (this.isSpaceChar(c)) {
                c = this.readByte();
            }
            boolean minus = false;
            if (c == '-') {
                minus = true;
                c = this.readByte();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res = res * 10 + c - '0';
                c = this.readByte();
            } while (!this.isSpaceChar(c));
            return minus ? -res : res;
        }

        public long nextLong() {
            if (!this.hasNext()) {
                throw new NoSuchElementException();
            }
            int c = this.readByte();
            while (this.isSpaceChar(c)) {
                c = this.readByte();
            }
            boolean minus = false;
            if (c == '-') {
                minus = true;
                c = this.readByte();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res = res * 10 + c - '0';
                c = this.readByte();
            } while (!this.isSpaceChar(c));
            return minus ? -res : res;
        }

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

        public int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = this.nextInt();
            }
            return a;
        }

        public long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = this.nextLong();
            }
            return a;
        }

        public char[][] nextCharMap(int n, int m) {
            char[][] map = new char[n][m];
            for (int i = 0; i < n; i++) {
                map[i] = this.next().toCharArray();
            }
            return map;
        }
    }

    static void tr(Object... o) {
        out.println(Arrays.deepToString(o));
    }
}
