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: isize = iter.next().unwrap().parse().unwrap();
    let h: isize = iter.next().unwrap().parse().unwrap();
    let n: isize = iter.next().unwrap().parse().unwrap();
    
    let mut has_drawn_s: Vec<bool> = vec![false; w as usize];
    let mut has_drawn_n: Vec<bool> = vec![false; h as usize];
    
    let mut count = 0;
    while count < n {
        let s: usize = iter.next().unwrap().parse().unwrap();
        let k: usize = iter.next().unwrap().parse().unwrap();
        
        has_drawn_s[s-1] = true;
        has_drawn_n[k-1] = true;
        
        count += 1;
    }
    let n_suit: isize = has_drawn_s
        .iter()
        .fold(0_isize, |acc, &b| if b {acc+1} else {acc});
    let n_num: isize = has_drawn_n
        .iter()
        .fold(0_isize, |acc, &b| if b {acc+1} else {acc});
    
    let n_matched: isize = n_suit*h + n_num*w - n_suit*n_num - n;
    println!("{}", n_matched);
}