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Problem
Two natural numbers `n` and `d` (with `0 <= d <= 9`) are read. Print how many times the digit `d` appears in the decimal representation of `n`, using **a recursive function**.
Define a recursive function `count(n, d)` that returns the number of occurrences of digit `d` in `n`:
```
count(0, d) = 0
count(n, d) = (n % 10 == d ? 1 : 0) + count(n / 10, d), for n > 0
```
Special case `n == 0`: if `d == 0`, the answer is `1` (the number 0 has one digit, which is 0); otherwise the answer is `0`.
Input format
Input
input.txt
The program reads from standard input two natural numbers `n` and `d`, separated by a space, with `0 <= d <= 9`. - `0 <= n <= 1.000.000.000` - `0 <= d <= 9` - The solution must use recursion.
Output format
Output
output.txt
The program prints a single natural number: how many times digit `d` appears in `n`, followed by a newline.
Example
input
112233 2
output
2
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Sample cases (from the problem)
Sample Case 1
Input
112233 2
Expected output
2
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