import sys

sys.setrecursionlimit(10 ** 6)
int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def MI(): return map(int, sys.stdin.readline().split())
def MI1(): return map(int1, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]

def main():
    w=int(input())
    h=int(input())
    n=int(input())
    ss=set()
    kk=set()
    for _ in range(n):
        s,k=MI()
        ss.add(s)
        kk.add(k)
    ans=h*len(ss)+w*len(kk)-len(ss)*len(kk)-n
    print(ans)

main()