Contains a Seven

Difficulty: 1900 4000 ms 128 MB

digit-dp

Count integers in [L, R] whose decimal form contains at least one digit 7.

Input: one line with two integers L and R.

Output: the count in [L, R].

Constraints:

• 1 ≤ L ≤ R ≤ 10¹⁸

Sample Tests

1 20

2

70 80

10

Read the Editorial