H = int(input())
W = int(input())
N = int(input())

row = set()
col = set()
for _ in range(N):
    a, b = map(int, input().split())
    row.add(a)
    col.add(b)

ans = H * len(col) + W * len(row)
ans -= len(col) * len(row)
ans -= N
print(ans)