import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Main p = new Main();
	}

	public Main() {
		Scanner sc = new Scanner(System.in);
		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();
		}
		solve(w, h, s, k);
	}

	public void solve(int W, int H, int[] s, int[] k) {
		boolean[] mark = new boolean[W+1];
		boolean[] number = new boolean[H+1];
		
		for(int i=0;i<s.length;i++){
			mark[s[i]] = true;
			number[k[i]] = true;
		}
		
		long markNum = 0;
		for(int i=0;i<mark.length;i++){
			if(mark[i])
				markNum++;
		}
		long numNum = 0;
		for(int i=0;i<number.length;i++){
			if(number[i])
				numNum++;
		}

		long res = markNum*H+numNum*W-markNum*numNum-s.length;
		
		System.out.println(res);
		
	}

}