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We have a **sorted** set of digits `D`

, a non-empty subset of `{'1','2','3','4','5','6','7','8','9'}`

.
(Note that `'0'`

is not included.)

Now, we write numbers using these digits, using each digit as many times as we want.
For example, if `D = {'1','3','5'}`

, we may write numbers
such as `'13', '551', '1351315'`

.

Return the number of positive integers that can be written (using the digits of
`D`

) that are less than or equal to `N`

.

**Example 1:**

Input:D = ["1","3","5","7"], N = 100Output:20Explanation:The 20 numbers that can be written are: 1, 3, 5, 7, 11, 13, 15, 17, 31, 33, 35, 37, 51, 53, 55, 57, 71, 73, 75, 77.

**Example 2:**

Input:D = ["1","4","9"], N = 1000000000Output:29523Explanation:We can write 3 one digit numbers, 9 two digit numbers, 27 three digit numbers, 81 four digit numbers, 243 five digit numbers, 729 six digit numbers, 2187 seven digit numbers, 6561 eight digit numbers, and 19683 nine digit numbers. In total, this is 29523 integers that can be written using the digits of D.

All contents and pictures on this website come from the Internet and are updated regularly every week. They are for personal study and research only, and should not be used for commercial purposes. Thank you for your cooperation.