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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.regex.Pattern;

public class Main {
    public void solve(BufferedReader stdin, PrintWriter stdout) throws NumberFormatException, IOException {
        int[] line = Pattern.compile(" ").splitAsStream(stdin.readLine()).mapToInt(Integer::parseInt).toArray();
        int n = line[0];
        int k = line[1];

        if (k == 1) {
            stdout.println(0);
            return ;
        }

        int min = 1;
        int max = n - (k - 1);
        stdout.println(max - min);
    }

    public static void main(String[] args) throws NumberFormatException, IOException {
        BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter stdout = new PrintWriter(System.out, false);
        new Main().solve(stdin, stdout);
        stdout.flush();
    }
}
