import sys sys.setrecursionlimit(10**7) 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()) H,W,Q = MI() YX = [] A = {} for _ in range(Q): Y,X = MI() YX.append((Y,X)) A[X] = H+1 ans = H*W for i in range(Q): Y,X = YX[i] if A[X] > Y: ans -= A[X]-Y A[X] = Y print(ans)