# coding=utf-8
''' If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000. '''


def calc(n, a):
  tmp = n / a
  return (tmp + 1) * tmp * a / 2

x = 3
y = 5
maxx = 1000

out = calc(maxx, x) + calc(maxx, y) - calc(maxx, x * y)

print out


'''
total = 0
for i in range(1000):
  if i % 3 == 0 or i % 5 == 0: # 条件为能被 3 或 5 整除
    total += i # 足条件的数字加入到 total 中
print total
'''