use std::collections::{HashMap, HashSet};

fn main() {
    proconio::input! {
        w: usize,
        h:usize,
        n:usize,
        sk: [(u64, u64); n],
    }
    let mark: HashSet<u64> = HashSet::from_iter(sk.iter().map(|x| x.0));
    let numbers: HashSet<u64> = HashSet::from_iter(sk.iter().map(|x| x.1));
    println!("{}", w * h - (w - mark.len()) * (h - numbers.len()) - n);
}