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.util.Scanner;

public class Main {

	static Scanner scanner;
	public static void main(String[] args) {
	    scanner = new Scanner(System.in);

	    int n=gi();
	    int k=gi();

	    
	    //System.out.print(a-b+1);
	    if (k==1) {
	    	System.out.print(0);
	    }else {
	    	System.out.print(n-k);
	    }



	}

	public static long d(long n) {
		String a=String.valueOf(n);
		return (long)a.length();
	}

	// 文字列として入力を取得
	public static String gs() {
		return scanner.next();
	}

	// intとして入力を取得
	public static int gi() {
		return Integer.parseInt(scanner.next());
	}

	// longとして入力を取得
	public static long gl() {
		return Long.parseLong(scanner.next());
	}

	// doubleとして入力を取得
	public static double gd() {
		return Double.parseDouble(scanner.next());
	}
}