In this task, you need to count the number of times the given letter appears in the given sentence.

Input: Consider Input: Sentence: 'a red train traveling down train tracks near a forest'. Find frequency of the letter 'f'

Output: 1


Input: Consider Input: Sentence: 'many white birds flying above a river that flows in front of a forest'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'two zebra stand near the wooden posts on a building'. Find frequency of the letter 't'


Output: 4