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

Input: Consider Input: Sentence: 'the miniature, elaborate exhibit depicts an ancient boating scene'. Find frequency of the letter 'n'

Output: 6

Input: Consider Input: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'

Output: 1

Input: Consider Input: Sentence: 'many public transit buses in a city street'. Find frequency of the letter 'a'
Output: 3