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.*;
import java.util.*;
import java.util.Map.Entry;
import java.util.function.Function;
import java.util.stream.Collectors;

@SuppressWarnings("unused")
public class Main {
	String fileName = "input.txt";
	final boolean isDebug = false;
	//final boolean isDebug = true;
	FastScanner in = new FastScanner(System.in);
	PrintWriter out = new PrintWriter(System.out);
	final int MOD = (int)1e9+7;
	final long INF = Long.MAX_VALUE / 2;
	//final int INF = Integer.MAX_VALUE / 2;
	
	//System.out.println();はつかわない！！
	void solve() throws Exception{
		int N = in.nextInt(), K = in.nextInt();
		if(K != 1) out.println((N - K));
		else out.println("0");
	}
	
	/* end solve */
	
	/* main */
	public static void main(String[] args) throws Exception {
		new Main().m();
	}
	
	void m() throws Exception {
		if(isDebug) in = new FastScanner(new FileInputStream(fileName));
		solve();
		out.flush();
	}
	/* end main */
}
/* end Main */

class FastScanner {
	Reader input;

	FastScanner() {this(System.in);}
	FastScanner(InputStream stream) {this.input = new BufferedReader(new InputStreamReader(stream));}
	
	int nextInt() {return (int) nextLong();}

	long nextLong() {
		try {
			int sign = 1;
			int b = input.read();
			while ((b < '0' || '9' < b) && b != '-' && b != '+') {
				b = input.read();
			}
			if (b == '-') {
				sign = -1;
				b = input.read();
			} else if (b == '+') {
				b = input.read();
			}
			long ret = b - '0';
			while (true) {
				b = input.read();
				if (b < '0' || '9' < b) return ret * sign;
				ret *= 10;
				ret += b - '0';
			}
		} catch (IOException e) {
			e.printStackTrace();
			return -1;
		}
	}

	double nextDouble() {
		try {
			double sign = 1;
			int b = input.read();
			while ((b < '0' || '9' < b) && b != '-' && b != '+') {
				b = input.read();
			}
			if (b == '-') {
				sign = -1;
				b = input.read();
			} else if (b == '+') {
				b = input.read();
			}
			double ret = b - '0';
			while (true) {
				b = input.read();
				if (b < '0' || '9' < b) break;
				ret *= 10;
				ret += b - '0';
			}
			if (b != '.') return sign * ret;
			double div = 1;
			b = input.read();
			while ('0' <= b && b <= '9') {
				ret *= 10;
				ret += b - '0';
				div *= 10;
				b = input.read();
			}
			return sign * ret / div;
		} catch (IOException e) {
			e.printStackTrace();
			return Double.NaN;
		}
	}

	char nextChar() {
		try {
			int b = input.read();
			while (Character.isWhitespace(b)) {
				b = input.read();
			}
			return (char) b;
		} catch (IOException e) {
			e.printStackTrace();
			return 0;
		}
	}

	String nextStr() {
		try {
			StringBuilder sb = new StringBuilder();
			int b = input.read();
			while (Character.isWhitespace(b)) {
				b = input.read();
			}
			while (b != -1 && !Character.isWhitespace(b)) {
				sb.append((char) b);
				b = input.read();
			}
			return sb.toString();
		} catch (IOException e) {
			e.printStackTrace();
			return "";
		}
	}
}