from collections import defaultdict
w=int(input())
h=int(input())
n=int(input())
l=[list(map(int,input().split())) for i in range(n)]
d=defaultdict(int)
for i in range(n):
  d[l[i][0]*10**8+l[i][1]]=1
L1=set()
L2=set()
for i in range(n):
  L1.add(l[i][0])
  L2.add(l[i][1])
L1=list(L1)
L2=list(L2)
ans=len(L1)*h+len(L2)*w-len(L1)*len(L2)
for i in range(len(L1)):
  for j in range(len(L2)):
    if d[L1[i]*10**8+L2[j]]==1:
      ans-=1
print(ans)