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

Input: Consider Input: Sentence: 'a girl sits on a surfboard and smiles'. Find frequency of the letter 'i'

Output: 3


Input: Consider Input: Sentence: 'an orange cat sitting on the ground next to a  purse'. Find frequency of the letter 's'

Output: 2


Input: Consider Input: Sentence: 'a cat is standing on its back legs to reach a person's hand holding an apple core'. Find frequency of the letter 'c'


Output: 4