W = int(raw_input())
H = int(raw_input())
N = int(raw_input())
S,K = set([]),set([])
ans = 0
for num in xrange(N):
    s,k = map(int,raw_input().split())
    if   s in S and k in K: ans -= 1
    elif s in S: ans += W-len(S)-1
    elif k in K: ans += H-len(K)-1
    else:
        ans += W+H-len(S)-len(K)-2
    S.add(s)
    K.add(k)
print ans