use std::env;
use std::io::prelude::*;
use std::io;
use std::fs::File;
use std::str::FromStr;
use std::io::BufReader;
fn buf_read() -> io::Result<(Vec<String>)> {
    let args: Vec<_> = env::args().collect();
    if args.len() >= 2 {
        let f = try!(File::open("input.txt"));
        let input_lines: Vec<_> = BufReader::new(f).lines().collect();
        let lines: Vec<String> = input_lines.into_iter().map(|e| e.unwrap()).collect();
        Ok((lines))
    } else {
        let stdin = io::stdin();
        let input_lines: Vec<_> = stdin.lock().lines().collect();
        let lines: Vec<String> = input_lines.into_iter().map(|e| e.unwrap()).collect();
        Ok((lines))
    }
}

fn main() {
    type Element = usize;
    let input = buf_read().unwrap();
    let mut input_vectors: Vec<Vec<Element>> = vec![];
    for input_line in input {
        let input_str: Vec<String> = input_line.split(' ').map(String::from).collect();
        let mut input_vector: Vec<Element> = vec![];
        for input_elem_str in input_str {
            let elem: Element = Element::from_str(input_elem_str.as_str()).unwrap();
            input_vector.push(elem);
        }
        input_vectors.push(input_vector);
    }
    let x_len = input_vectors[0][0];
    let y_len = input_vectors[0][1];
    let mut area: Vec<Vec<Element>> = vec![vec![0; x_len]; y_len];
    for i in 1..input_vectors[0][2] + 1 {
        match input_vectors[i][2] {
            1 => {
                for y in 0..y_len {
                    for x in 0..input_vectors[i][0] {
                        area[y][x] = 1;
                    }
                }
            }
            2 => {
                for y in 0..y_len {
                    for x in input_vectors[i][0]..x_len {
                        area[y][x] = 1;
                    }
                }
            }
            3 => {
                for x in 0..x_len {
                    for y in 0..input_vectors[i][1] {
                        area[y][x] = 1;
                    }
                }
            }
            _ => {
                for x in 0..x_len {
                    for y in input_vectors[i][1]..y_len {
                        area[y][x] = 1;
                    }
                }
            }
        }
    }
    let black_sum: usize = area.into_iter()
                               .fold(0, |acc, ref x| acc + x.into_iter().sum::<usize>());
    println!{"{:?}", x_len * y_len - black_sum}
}
