W, H, N = [int(input()) for _ in range(3)]
pw = [0]*(W+1)
ph = [0]*(H+1)
for _ in range(N):
        w, h = map(int,input().split())
        pw[w]=1
        ph[h]=1
ws = sum(pw)
hs = sum(ph)
n = W*hs + ws*H - ws*hs -N
print(n)