cox,coy=1,1
W=int(input())
H=int(input())
n=int(input())
out=0
w=[]
h=[]
for i in range(n):
	x,y=map(int,input().split())
	a,b=0,0
	for j in range(i):
		if w[j]==x:a=1
		if h[j]==y:b=1
	w.append(x)
	h.append(y)
	if a+b==2:out-=1
	if a==0:out+=H-coy
	if b==0:out+=W-cox
	if a==0:cox+=1
	if b==0:coy+=1
print(out)