w=int(input())
h=int(input())
n=int(input())

array=[[0 for i in range(h+10)] for j in range(w+10)]
sum=0
for j in range(n):
    a,b=[int(i) for i in input().split()]
    if array[a][b]==1:
        sum-=1
    array[a][b]=-1
    for i in range(1,h+1):
        if array[a][i]==0: sum+=1
        if array[a][i]!=-1: array[a][i]=1
    for i in range(1,w+1):
        if array[i][b]==0: sum+=1
        if array[i][b]!=-1: array[i][b]=1
print(sum)