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

pub fn main() {
    let i = stdin();
    let mut o = Vec::new();
    run(i.lock(), &mut o);
    stdout().write_all(&o).unwrap();
}

fn run<R: BufRead, W: Write>(i: R, o: &mut W) {
    let mut i = ReadEx::from(i);
    let w = i.read::<usize>();
    let h = i.read::<usize>();
    let n = i.read::<usize>();
    let mut sk = Vec::new();
    for _ in 0..n {
        sk.push(i.read2::<usize, usize>());
    }
    writeln!(o, "{}", solve(w, h, &sk)).unwrap();
}
fn solve(w: usize, h: usize, sk: &[(usize, usize)]) -> usize {
    let mut ss = HashSet::new();
    let mut ks = HashSet::new();
    for sk in sk {
        ss.insert(sk.0);
        ks.insert(sk.1);
    }
    h * ss.len() + w * ks.len() - ss.len() * ks.len() - sk.len()
}

mod utils {
    use super::*;

    pub struct ReadEx<R: BufRead> {
        r: R,
        s: String,
    }

    macro_rules! fn_read {
        {$f:ident($($v:ident: $t:ident),*)} => {
            pub fn $f<$($t: FromStr),*>(&mut self) -> ($($t),*) {
                let i = &mut self.read_line().split(' ');
                $(
                    let $v = next(i);
                )*
                ($($v),*)
            }
        };
    }

    impl<R: BufRead> ReadEx<R> {
        pub fn from(r: R) -> Self {
            ReadEx {
                r: r,
                s: String::new(),
            }
        }
        pub fn read_line(&mut self) -> &str {
            self.s.clear();
            self.r.read_line(&mut self.s).unwrap();
            self.s.trim()
        }

        pub fn read<T: FromStr>(&mut self) -> T {
            self.read_line().parse().ok().unwrap()
        }
        fn_read! { read2(v1: T1, v2: T2) }
    }

    fn next<'a, T: FromStr, I: std::iter::Iterator<Item = &'a str>>(i: &mut I) -> T {
        i.next().unwrap().parse().ok().unwrap()
    }

}