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

Input: Consider Input: Sentence: 'a small boat and a large boat on a river near a city'. Find frequency of the letter 'a'

Output: 10


Input: Consider Input: Sentence: 'several zebras  and a giraffe in an enclosure'. Find frequency of the letter 's'

Output: 3


Input: Consider Input: Sentence: 'a close up of a cat laying on an open luggage bag'. Find frequency of the letter 'p'


Output: 2