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

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: 'a table topped with a cupcake on a picture of a cupcake'. Find frequency of the letter 'o'

Output: 3


Input: Consider Input: Sentence: 'a polar bear stands on some rocks'. Find frequency of the letter 'a'


Output: 4