w = int(raw_input())
lw = [False for _ in range(w)]
h = int(raw_input())
lh = [False for _ in range(h)]
n = int(raw_input())
c = 0
for _ in range(n):
    s,k = map(int, raw_input().split())
    lw[s-1] = True
    lh[k-1] = True
wt = lw.count(True)
ht = lh.count(True)
print wt * h - n + (w-wt) * ht