From 1 to 1000, how many numbers can be divided by 3 or 7

From 1 to 1000, how many numbers can be divided by 3 or 7

1000 △ 3 = more than 333 1
That is, 333 can be divided by 3
1000 △ 7 = 142 more than 6
That is, 142 can be divided by 7
1000 △ 21 = 47,13
That is, 47 can be divided by 3 and 7 at the same time
Then, what can be divisible by 3 or by 7 are:
333 + 142-47 = 428