W = int(input())
H = int(input())
N = int(input())
l = [[] for i in range(W)]
s = set([])

for i in range(N):
    mark, num = map(int, input().split())
    l[mark - 1].append(num)
    s.add(num)

s_len = len(s)
ans = 0
for l_i in l:
    if len(l_i) == 0:
        ans += s_len
    else:
        ans += H - len(l_i)
print(ans)