use std::io::Read;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let w: u64 = itr.next().unwrap().parse().unwrap();
    let h: u64 = itr.next().unwrap().parse().unwrap();
    let n: usize = itr.next().unwrap().parse().unwrap();

    let mut st1 = std::collections::HashSet::new();
    let mut st2 = std::collections::HashSet::new();
    for _ in 0..n {
        let s: u64 = itr.next().unwrap().parse().unwrap();
        let k: u64 = itr.next().unwrap().parse().unwrap();
        st1.insert(s);
        st2.insert(k);
    }
    println!(
        "{}",
        w * h - (w - st1.len() as u64) * (h - st2.len() as u64) - n as u64
    );
}