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

Input: Consider Input: Sentence: 'a dog is shown sitting on rocks by the beach'. Find frequency of the letter 'a'

Output: 2


Input: Consider Input: Sentence: 'a bed with a mattress that has nothing on it'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'a laptop with an i love sticker on the front and google in the back'. Find frequency of the letter 'i'


Output: 4