#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
import bisect
import heapq


def input():
    return sys.stdin.readline()[:-1]


# sys.setrecursionlimit(1000000)

# _INPUT = """3
# 2
# 2
# 1 1
# 2 1
# """
# sys.stdin = io.StringIO(_INPUT)


W = int(input())
H = int(input())
N = int(input())
W_set = set()
H_set = set()
for _ in range(N):
    S, K = map(int, input().split())
    S -= 1
    K -= 1
    W_set.add(S)
    H_set.add(K)

n1 = len(W_set)
n2 = len(H_set)
ans = n1*H + n2*W - n1*n2 - N
print(ans)