import sys input = sys.stdin.readline H, W, Q = map(int, input().split()) qs = [tuple(map(int, input().split())) for _ in range(Q)] xs = [q[1] for q in qs] def compress(init_val): t = sorted(set(init_val)) d = dict([[t[i], i] for i in range(len(t))]) res = [0] * len(init_val) for i in range(len(init_val)): res[i] = d[init_val[i]] return res cxs = compress(xs) mx = max(cxs) table = [H] * (mx + 1) res = H * W for i in range(Q): x = cxs[i] y = qs[i][0] - 1 res -= max(0, table[x] - y) table[x] = min(table[x], y) print(res)