You are given a range \(L\) to \(R\). You are required to find the number of \(k\)-special numbers in this range (inclusive). A \(k\)-special number is a number that has exactly \(k\) unique digits.

For example:

• 26 is a 2-special number. Digits 2 and 6 are unique.
• 6643 is a 3-special number. Digits 6, 4, and 3 are unique.

Constraints
\(1 \le T \le 10\\ 1 \le L,\ R \le 10^{18}\\ 1 \le k \le 7\)