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

Input: Consider Input: Sentence: 'a person does a trick on a ramp on a snowboard'. Find frequency of the letter 's'

Output: 3

Input: Consider Input: Sentence: 'a bed with a dog laying on it next to two laptop computers'. Find frequency of the letter 'n'

Output: 3

Input: Consider Input: Sentence: 'a laptop and a desk lamp left on alone in a room'. Find frequency of the letter 'd'
Output: 2