W = int(input())#マークの種類
H = int(input())#数字カードの最大値
N = int(input())
SK = [0 for _ in range(N)]
A = set()
B = set()
for i in range(N):
    a,b = map(int,input().split())
    A.add(a)
    B.add(b)
    SK[i] = [a,b]
#マーク順に並べる
SK.sort()
ans = 0
i = 0
while i < N:
    s = SK[i][0]
    k = SK[i][1]
    cntK = 1
    i += 1
    if i == N:
        ans += H-cntK
        break
    #マークが同じカードが何枚あるかをcntに格納
    while SK[i][0] == s:
        cntK += 1
        i += 1
        if i == N:
            ans += H-cntK
            break
    ans += H-cntK if i != N else 0
if W > len(B):
    ans += (W-len(B))*len(A)
print(ans)