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

Input: Consider Input: Sentence: 'town clocks affixed to a tall, brick building'. Find frequency of the letter 'r'

Output: 1

Input: Consider Input: Sentence: 'two zebras standing around while a third zebra drinks from a pond'. Find frequency of the letter 's'

Output: 3

Input: Consider Input: Sentence: 'a classic motorcycle is parked in a driveway'. Find frequency of the letter 'c'
Output: 4