def main():
    w, h, n = [int(input()) for i in range(3)]

    soot, no = [0] * w, [0] * h
    for i in range(n):
        s, k = map(int, input().split())
        soot[s-1] = no[k-1] = 1

    ans, used_no = 0, sum(no)
    
    for i in range(w):
        if soot[i]:
            ans += h
        else:
            ans += used_no

    print(ans-n)


if __name__ == '__main__':
    main()