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

Input: Consider Input: Sentence: 'a burning wood stove has a tea pot sitting on top of it and is full of wood'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'small black bird with red on its head standing on a tree branch'. Find frequency of the letter 'b'

Output: 3


Input: Consider Input: Sentence: 'three people are sitting on a bench looking over a pier'. Find frequency of the letter 'b'


Output: 1