w = int(input())
h = int(input())
n = int(input())
havew = [False] * w
haveh = [False] * h
for _ in range(n):
    s, k = map(int, input().split())
    havew[s-1] = True
    haveh[k-1] = True
sw = sum(havew)
sh = sum(haveh)
ans = sw * h + sh * w - sw * sh - n
print(ans)