The Hedgehog likes to give presents to his friend, but no less he likes to receive them.

Having received another present today, the Hedgehog suddenly understood that he has no place to put it as there was no room left on the special shelf in the cupboard. He will have to choose another shelf, but which one should he choose, how large should it be?

In order to get to know this, the Hedgehog asks you to write him a program that will count the estimated number of presents that he will receive during the following N days. Besides, he is guided by the principle: 

  * on each holiday day the Hedgehog will necessarily receive a present, 
  * he receives presents at least every K days (i.e., if he received a present on the i-th day, he will receive the next present no later than on the i + K-th day). 



For the given N and K, as well as the list of holidays among the following N days count the minimal number of presents that could be given to the Hedgehog. The number of today's day is zero, and you should regard today's present as already given (i.e., you shouldn't count it in the answer).

Input

The first line contains integers N and K (1 ≤ N ≤ 365, 1 ≤ K ≤ N).

The second line contains a number C which represents the number of holidays (0 ≤ C ≤ N). Then in the same line follow C numbers ranging from 1 to N which are the numbers of holiday days. The numbers are given in the increasing order, without repeating numbers among them.

Output

Print a single number — the minimal number of presents the Hedgehog will receive over the following N days.

Examples

Input

5 2
1 3


Output

3

Input

10 1
3 6 7 8


Output

10
import java.io.OutputStreamWriter;
import java.io.BufferedWriter;
import java.util.Comparator;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Random;
import java.io.Writer;
import java.util.HashSet;
import java.util.List;
import java.io.IOException;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.ArrayList;
import java.util.NoSuchElementException;
import java.util.TreeSet;
import java.math.BigInteger;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author Alex
 */
public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		OutputWriter out = new OutputWriter(outputStream);
		TaskA solver = new TaskA();
		solver.solve(1, in, out);
		out.close();
	}
}

class TaskA {
    public void solve(int testNumber, InputReader in, OutputWriter out) {
	    int n = in.ri(), k = in.ri(), c = in.ri();
	    HashSet<Integer> holidays = new HashSet<>(); for(int i = 0; i < c; i++)  holidays.add(in.ri()); 
	    boolean[] days = new boolean[n + 1];
	    days[0] = true;
	    for(int i = 1; i <= n; i++) {
		    if (holidays.contains(i)){
			    days[i] = true;
		    }
		    else{
			    boolean ok = false;
			    for(int j = i - k + 1; j < i; j++) if (j >= 0 && days[j]) ok = true;
			    if (!ok) days[i] = true;
		    }
	    }
	    out.printLine(ArrayUtils.count(days, true) - 1);
    }
}

class InputReader {
	private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar;
	private int numChars;
	private SpaceCharFilter filter;

	public InputReader(InputStream stream) {
		this.stream = stream;
	}

	public int read() {
		if (numChars == -1)
			throw new InputMismatchException();
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}
	public int ri(){
		return readInt();
	}

	public int readInt() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}
	public boolean isSpaceChar(int c) {
		if (filter != null)
			return filter.isSpaceChar(c);
		return isWhitespace(c);
	}

	public static boolean isWhitespace(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}
	public interface SpaceCharFilter {
		public boolean isSpaceChar(int ch);
	}
}

class OutputWriter {
	private final PrintWriter writer;

	public OutputWriter(OutputStream outputStream) {
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
	}
	public void close() {
		writer.close();
	}
	public void printLine(int i) {
		writer.println(i);
	}

}

class ArrayUtils {
	public static int count(boolean[] array, boolean value) {
		int result = 0;
		for (boolean i : array) {
			if (i == value)
				result++;
		}
		return result;
	}
}

