You are given a group of distinct k characters(from a-z). Construct a string of length n such that:
No two consecutive positions in string contain the same character
The odd positions can only contain characters from initial group of k characters
Even positions can contain any character from a to z.
Indexing is 1 based. Find number of distinct ways to form such strings modulo 10^9+7.
Given two numbers L and R. Determine count of numbers in range [L,R] such that their number of divisors is prime.