import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	W = int(input())
	H = int(input())
	N = int(input())
	Dw = defaultdict(int)
	Dh = defaultdict(int)
	for i in range(N):
		S, K = getlist()
		if Dw[S] == 0:
			Dw[S] = H - 1
		else:
			Dw[S] -= 1

		if Dh[K] == 0:
			Dh[K] = W - 1
		else:
			Dh[K] -= 1

	ans = len(Dw) * H + len(Dh) * W - len(Dh) * len(Dw) - N
	print(ans)




if __name__ == '__main__':
	main()