#![allow(unused_imports)]

use std::io::{self, BufRead};
use std::str::FromStr;
use std::collections::*;
use std::cmp::*;

#[allow(dead_code)]
struct Parser<'a> {
    tokens: &'a mut Iterator<Item = String>,
}
#[allow(dead_code)]
impl<'a> Parser<'a> {
    fn new(i: &'a mut Iterator<Item = String>) -> Self {
        Parser {tokens: i}
    }
    fn take<T: FromStr>(&mut self) -> T {
        match self.tokens.next().expect("empty iterator").parse() {
            Ok(x) => x,
            Err(_) => panic!()
        }
    }

    fn take_some<T: FromStr>(&mut self, n: usize) -> Vec<T> {
        self.tokens.take(n).map(|s| match s.parse() { Ok(x) => x, Err(_) => panic!() } ).collect()
    }
}

//sieve[k] is true if k is a prime
//[0, n)
#[allow(dead_code)]
fn sieve_of_eratosthenes(n: u64) -> Vec<bool> {
    let mut v = vec![true; n as usize];
    v[0] = false;
    v[1] = false;
    for i in 2..n {
        if !v[i as usize] {
            continue;
        }
        let mut j = 2*i;
        while j < n {
            v[j as usize] = false;
            j += i;
        }
    }
    v
}

#[allow(dead_code)]
fn vec_2d<T>(n: usize, m: usize, t: T) -> Vec<Vec<T>> where T: Clone {
    let mut u = Vec::new();
    let mut v = Vec::new();
    v.resize(m, t);
    u.resize(n, v);
    u
}

fn main() {
    let stdin = io::stdin();
    let mut tokens = stdin.lock().lines().filter_map(|x| x.ok()).flat_map(|x| x.split_whitespace().map(|s| s.to_owned()).collect::<Vec<String>>());
    let mut parser = Parser::new(&mut tokens);

    let w: usize = parser.take();
    let h: usize = parser.take();
    let n: usize = parser.take();

    let mut ws = BTreeSet::new();
    let mut hs = BTreeSet::new();

    for _ in 0..n {
        let s: usize = parser.take();
        let k: usize = parser.take();
        ws.insert(s);
        hs.insert(k);
    }

    println!("{}", w*hs.len() + h*ws.len() - ws.len()*hs.len() - n);
}