from collections import defaultdict
W = int(input())
H = int(input())
N = int(input())
SK = [list(map(int, input().split())) for _ in range(N)]

d = defaultdict(list)
for k, v in SK:
    d[k].append(v)

mm = 0
b = set()
for dv in d.values():
    mm += H - len(dv)
    for dvv in dv:
        b.add(dvv)

h = len(list(d.keys()))
mn = (W - h) * len(b)
print(mm + mn)