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


public class Main {
	static int[] vy = {1,0,-1,0};
	static int[] vx = {0,1,0,-1};
	public static void main(String[] args) {	
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int W = sc.nextInt();
		int H = sc.nextInt();
		int N = sc.nextInt();
		int[] S = new int[N];
		int[] K = new int[N];
		for(int i = 0; i < N; i++) {
			S[i] = sc.nextInt();
			K[i] = sc.nextInt();
		}
		int[] s = new int[W+1];
		int[] k = new int[H+1];
		for(int i = 0; i < N; i++) {
			s[S[i]]++;
			k[K[i]]++;
		}
		long sum = 0;
		long uniqW = 0;
		long uniqH = 0;
		for(int i = 0; i <= W; i++) {
			if(s[i] != 0) {
				uniqW++;
			}
			
		}
		for(int i = 0; i <= H; i++) {
			if(k[i] != 0) {
				uniqH++;
			}
		}
		sum = H*uniqW + W*uniqH - uniqW*uniqH - N;
		System.out.println(sum);
		
		
	}
}