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

Input: Consider Input: Sentence: 'a sailboat is floating near the rocky shore of a beach'. Find frequency of the letter 'o'

Output: 5

Input: Consider Input: Sentence: 'a couple of men standing inside of a liquor store'. Find frequency of the letter 'p'

Output: 1

Input: Consider Input: Sentence: 'a red stop sign sitting on the side of a street'. Find frequency of the letter 's'
Output: 5