package main

import (
	"fmt"
)

func main() {
	solve11()
}

func solve11(){
	var W, H, N int
	fmt.Scan(&W, &H, &N)
	var s, k int
	spot := make([]int, W+1)
	num := make([]int, H+1)
	var Wsum, Hsum int
	for i:=1; i<=N; i++ {
	    fmt.Scan(&s, &k)
		if spot[s]==0{
			Wsum++
		}
		if num[k]==0{
			Hsum++
		}
		spot[s]=1
		num[k]=1
	}
	fmt.Println(W*H-(W-Wsum)*(H-Hsum)-N)
	//fmt.Println(spot, num)
}