w=int(input())
h=int(input())
n=int(input())
ans=0
tate=set()
yoko=set()

for i in range(n):
    wi,hi = map(int,input().split())
    if wi not in yoko:
        yoko.add(wi)
        ans += (h-len(tate))
        
    if hi not in tate:
        tate.add(hi)
        ans += (w-len(yoko))
              
print(ans-n)