# coding:UTF-8 import sys MOD = 10 ** 9 + 7 INF = float('inf') H, W, Q = list(map(int, input().split())) # スペース区切り連続数字 YX = [list(map(int, input().split())) for _ in range(Q)] # スペース区切り連続数字(行列) res = H * W x_set = set() for y, x in YX: x_set.add(x) x_list = [x for x in x_set] x_list.sort() x_dict = {} for i in range(len(x_list)): x_dict[x_list[i]] = i zan = [H] * len(x_list) for y, x in YX: idx = x_dict[x] t = y - 1 if zan[idx] > t: d = zan[idx] - t zan[idx] = t res -= d print("{}".format(res))