#!/usr/bin/env python3
# -*- coding: utf-8 -*-


def main():
    w = int(input())
    h = int(input())
    n = int(input())
    jen_suits = set()
    jen_numbers = set()
    for _ in range(n):
        suit, number = map(int, input().split())
        jen_suits.add(suit)
        jen_numbers.add(number)
    w0 = len(jen_suits)
    h0 = len(jen_numbers)
    print(w0 * h + h0 * w - w0 * h0 - n)


if __name__ == '__main__':
    main()