/* 
 *     Author:  srtry
 *     Created: 2025-05-10T22:12:14+09:00
 *     Coding:  utf-8-unix
 */

use proconio::input;
use std::io::{stdout,Write,BufWriter};
use std::collections::HashSet;

fn main() {
    input!{
        w:usize,
        h:usize,
        n:usize,
        sk:[[usize;2];n]
    }

    let out = stdout();
    let mut out = BufWriter::new(out.lock());

    let mut suit_set:HashSet<usize> = HashSet::new();
    let mut num_set:HashSet<usize> = HashSet::new();
    for card in sk.iter() {
        suit_set.insert(card[0]);
        num_set.insert(card[1]);
    }
    let ans:usize = suit_set.len()*h + num_set.len()*w - suit_set.len()*num_set.len() - n;
    write!(out, "{}", ans).unwrap();

}