import sys
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


W,H,N = I(),I(),I()
mark = set()
number = set()
for _ in range(N):
    S,K = MI()
    mark.add(S)
    number.add(K)

X,Y = len(mark),len(number)
ans = X*H+Y*W-X*Y-N
print(ans)