w = int(input())
h = int(input())
n = int(input())

wc , hc = 0 , 0
wl = [0] * (w + 1)
hl = [0] * (h + 1)
for i in range(n):
	s,k = map(int,input().split())
	if wl[s] == 0:
		wl[s] = 1
	if hl[k] == 0:
		hl[k] = 1

ws , hs = sum(wl) , sum(hl)

print(h * ws + w * hs - ws * hs - n)