def multi_in_num(limit, base):
    count = limit // base
    return (count + 1) * count * base // 2

def dual_multi_in_num(limit, a, b):
    return multi_in_num(limit, a) + multi_in_num(limit, b) - multi_in_num(limit, a * b)

print(dual_multi_in_num(1000 - 1, 3, 5))