import sys
input = sys.stdin.readline
w = int(input())
h = int(input())
n = int(input())
a = [[*map(int, input().split())] for _ in range(n)]

mark = [0 for i in range(w)]
num = [0 for i in range(h)]
for x in a:
    mark[x[0] - 1] = 1
    num[x[1] - 1] = 1
cnt1 = mark.count(1)
cnt2 = num.count(1)
ans = cnt1 * h + cnt2 * w - cnt1*cnt2 - n
print(ans)