# your code goes here
W=int(input())
H=int(input())
N=int(input())
S=[[int(i) for i in input ().split()] for i in range (N)]
T=[0]*W
L=[0]*H
for i in range (N):
 #   print (S)
    T[S[i][0]]+=1
    L[S[i][1]]+=1
C=0
Tw=0
for i in range(W):
    if T[i]>0:
        C+=H
        Tw+=1
for i in range(H):
    if L[i]>0:
        C+=W-Tw
C-=N
print(C)