use std::io::Read;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    
    let mut iter = buf.split_whitespace();
    
    let w: usize = iter.next().unwrap().parse().unwrap();
    let h: usize = iter.next().unwrap().parse().unwrap();
    let n: usize = iter.next().unwrap().parse().unwrap();
    
    let mut has_drawn_s: Vec<bool> = vec![false; w+1];
    let mut has_drawn_n: Vec<bool> = vec![false; h+1];
    let mut n_suit: usize = 0;
    let mut n_num: usize = 0;
    
    let mut count = 0;
    while count < n {
        let s: usize = iter.next().unwrap().parse().unwrap();
        let k: usize = iter.next().unwrap().parse().unwrap();
        
        if !has_drawn_s[s] {
            n_suit += 1;
            has_drawn_s[s] = true;
        }
        if !has_drawn_n[k] {
            n_num += 1;
            has_drawn_n[k] = true;
        }
        
        count += 1;
    }

    let n_matched: usize = n_suit*h + n_num*w - n_suit*n_num - n;
    println!("{}", n_matched);
}