#!/usr/bin/env python3
#fileencoding: utf-8

W = int(input())
H = int(input())
N = int(input())

total = 0
marks = set([])
nums = set([])
for _ in range(N):
    s, k = [int(i) for i in input().strip().split(" ")]
    if s not in marks:
        total += (H - 1 - len(nums))
        if k in nums:
            total += 1
        marks.add(s)
    else:
        total -= 1

    if k not in nums:
        total += (W - 1 - len(marks))
        if s in marks:
            total += 1
        nums.add(k)
    else:
        total -= 1

print(total)