A chessboard n × m in size is given. During the zero minute we repaint all the black squares to the 0 color. During the i-th minute we repaint to the i color the initially black squares that have exactly four corner-adjacent squares painted i - 1 (all such squares are repainted simultaneously). This process continues ad infinitum. You have to figure out how many squares we repainted exactly x times.

The upper left square of the board has to be assumed to be always black. Two squares are called corner-adjacent, if they have exactly one common point.

Input

The first line contains integers n and m (1 ≤ n, m ≤ 5000). The second line contains integer x (1 ≤ x ≤ 109).

Output

Print how many squares will be painted exactly x times.

Examples

Input

3 3
1


Output

4


Input

3 3
2


Output

1


Input

1 1
1


Output

1
/**
 * Created by IntelliJ IDEA.
 * User: shakhov
 * Date: 15.06.2011
 * Time: 15:22:46
 * To change this template use File | Settings | File Templates.
 */

//6
//86 402 133 524 405 610   6 4 1

import java.io.*;
import java.util.*;

public class CodeForces {
	double eps = 0.00001;

	public void solve() throws IOException {
		int n=nextInt();
		int m=nextInt();
		int k=nextInt()-1;
		
		int arr[]=new int[2];
		arr[0]=n-k*2;
		arr[1]=m-k*2;
		
		if(arr[0]<1 || arr[1]<1){
			out.print(0);
		} else if(arr[0]==1 && arr[1]==1){
			out.print(1);
			} else {
			out.print(arr[0]+arr[1]-2);
		}
		
		
	}

	private BufferedReader reader;
	private StringTokenizer tokenizer;
	private String separator;
	public PrintWriter out;

	public static void main(String[] args) throws IOException {
		// new CodeForces().run(new FileReader("input.txt"), new
		// FileWriter("output.txt"));
		new CodeForces().run(new InputStreamReader(System.in), new OutputStreamWriter(System.out));
	}

	public void run(Reader reader, Writer writer) {
		try {
			this.reader = new BufferedReader(reader);
			out = new PrintWriter(writer);
			tokenizer = new StringTokenizer("");
			separator = System.getProperty("line.separator");
			separator = Character.toString(separator.charAt(separator.length() - 1));
			long t1 = System.currentTimeMillis();
			solve();
			out.flush();
			reader.close();
			writer.close();
			long t2 = System.currentTimeMillis();
			System.err.println("Time = " + (t2 - t1));
		} catch (Exception e) {
			e.printStackTrace();
			System.exit(1);
		}
	}

	int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}

	long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}

	double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}

	String nextToken() throws IOException {
		while (tokenizer == null || !tokenizer.hasMoreTokens()) {
			tokenizer = new StringTokenizer(reader.readLine());
		}
		return tokenizer.nextToken();
	}

}