use std::io::*;
use std::str::FromStr;
use std::collections::HashSet;

#[allow(dead_code)]
fn get_line() -> String {
    let stdin = stdin();
    let mut line = String::new();
    stdin.lock().read_line(&mut line).expect("io error.");
    line.trim().to_string()
}

#[allow(dead_code)]
fn cast<T: FromStr>(s: &str) -> T {
    s.parse().ok().expect("parse error.")
}

#[allow(dead_code)]
fn get_vec<T: FromStr>() -> Vec<T> {
    (&get_line()).split(' ').map(cast::<T>).collect()
}

fn main() {
    let mut v: Vec<usize> = vec![0; 3];
    for i in 0..3 {
        v[i] = cast(&get_line());
    }
    let (w, h, n) = (v[0], v[1], v[2]);

    let mut s: Vec<HashSet<u64>> = vec![HashSet::new(); 2];

    for _ in 0..n {
        let p: Vec<u64> = get_vec();
        for i in 0..2 {
            s[i].insert(p[i]);
        }
    }

    println!("{}",
        w * h - (h - s[1].len()) * (w - s[0].len()) - n
    );
}