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.util.NoSuchElementException;
import java.util.Random;

public class Main {
    private static FastScanner sc = new FastScanner();
    private static boolean DEBUG_FLG = false;

    public static void main(String[] args) {
    	int N = sc.nextInt();
    	int K = sc.nextInt();
    	if(K == 1) {
    		System.out.println(0);
    	} else {
    		System.out.println(N-K);
    	}
    }

    static void debug(long... args) {
    	if(!DEBUG_FLG) return;
    	boolean flg = false;
    	for(long s : args) {
    		if(flg) System.out.print(" ");
    		flg = true;
    		System.out.print(s);
    	}
    	System.out.println();
    }

    static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;
        private boolean hasNextByte() {
            if(ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch(IOException e) {
                    e.printStackTrace();
                }
                if(buflen <= 0) {
                    return false;
                }
            }
            return true;
        }
        private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
        private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
        private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
        public boolean hasNext() { skipUnprintable(); return hasNextByte();}
        public String next() {
            if (!hasNext()) throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while(isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }
        public long nextLong() {
            return Long.parseLong(next());
        }
        public int nextInt(){
            return Integer.parseInt(next());
        }
        public double nextDouble(){
            return Double.parseDouble(next());
        }
    }

    static void shuffleArray(long[] arr){
        int n = arr.length;
        Random rnd = new Random();
        for(int i=0; i<n; ++i){
            long tmp = arr[i];
            int randomPos = i + rnd.nextInt(n-i);
            arr[i] = arr[randomPos];
            arr[randomPos] = tmp;
        }
    }
}
