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

w_array=[0 for i in range(w+1)]
h_array=[0 for i in range(h+1)]
w_w=0
h_h=0
for j in range(n):
    a,b=[int(i) for i in input().split()]
    if w_array[a]==0:
        w_w+=1
        w_array[a]=1
    if h_array[b]==0:
        h_h+=1
        h_array[b]=1
print(h*w_w+w*h_h-w_w*h_h-n)