import sys
input=lambda:sys.stdin.readline().rstrip()
W,H,N=[int(input()) for i in range(3)]
A=[set() for i in range(2)]
for i in range(N):
	temp=list(map(int,input().split()))
	for j in range(2):
		A[j].add(temp[j])
print((len(A[0])-W)*(-len(A[1])+H)+W*H-N)