import javautilScanner;public class p1628 public static void mainString args Scanner scanner = new ScannerSystemin; int m = scannernextInt; int n = scannernextInt; int

import java.util.Scanner;

public class Main { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); int m = scanner.nextInt(); int n = scanner.nextInt(); int k = scanner.nextInt(); boolean[][] black = new boolean[m+1][n+1]; for (int i = 0; i < k; i++) { int xi = scanner.nextInt() - 1; int yi = scanner.nextInt() - 1; black[xi][yi] = true; }

    int curLen = 0;
    int count = 0;
    for (int i = 0; i < m; i++) {
        curLen = 0;
        for (int j = 0; j < n; j++) {
            if (!black[i][j]) {
                curLen++;
            } else {
               if(curLen>1)count++;
               if(curLen==1&&i<m-1&&black[i+1][j])count++;
                curLen = 0;
            }
            if(j==n-1&&(curLen>1||(curLen==1&&i<m-1&&black[i+1][j])))count++;
        }

    }

    for (int j = 0; j < n; j++) {
        curLen = 0;
        for (int i = 0; i < m; i++) {
            if (!black[i][j]) {
                curLen++;
            } else {
                if(curLen>1)count++;
                curLen = 0;
            }
            if(i==m-1&&curLen>1)count++;
        }


    }
    System.out.println(count);
}