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

Input: Consider Input: Sentence: 'a car accident has slowed traffic as a clean up crew works'. Find frequency of the letter 'f'

Output: 2


Input: Consider Input: Sentence: 'a woman at a table checking her cell phone'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'two computers and a laptop set up on a desk'. Find frequency of the letter 'r'


Output: 1