package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func Scanner() string {
	sc.Scan()
	return sc.Text()
}
func main() {
	buf := make([]byte, 0)
	sc.Buffer(buf, 100000007)
	sc.Split(bufio.ScanWords)
	w, _ := strconv.Atoi(Scanner())
	h, _ := strconv.Atoi(Scanner())
	n, _ := strconv.Atoi(Scanner())
	s := make([]int, n)
	k := make([]int, n)
	for i := 0; i < n; i++ {
		s[i], _ = strconv.Atoi(Scanner())
		k[i], _ = strconv.Atoi(Scanner())
	}
	mark := make([]int, w+1)
	num := make([]int, h+1)
	count := 0
	count2 := 0
	for i := 0; i < n; i++ {
		if mark[s[i]] == 0 {
			count++
		}
		if num[k[i]] == 0 {
			count2++
		}
		mark[s[i]] = 114514
		num[k[i]] = 114514
	}
	fmt.Println(w*h - (h-count2)*(w-count) - n)
}