w = int(input())
h = int(input())
n = int(input())
skn = [None] * n
for i in range(n):
    skn[i] = list(map(int, input().split(' ')))


hc = [False] * h
wc = [False] * w
for sk in skn:
    wc[sk[0] - 1] = True
    hc[sk[1] - 1] = True


hcount = hc.count(True)
wcount = wc.count(True)

result = hcount * w + wcount * h - hcount * wcount - n
print(result)