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

Input: Consider Input: Sentence: 'pedestrians pass by a stop sign, some holding surfboards'. Find frequency of the letter 'n'

Output: 3


Input: Consider Input: Sentence: 'a teddy bear is sitting on a heart shaped patio chair outside'. Find frequency of the letter 'i'

Output: 6


Input: Consider Input: Sentence: 'three elephants walking through the grass on a sunny day'. Find frequency of the letter 'a'


Output: 5