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

Input: Consider Input: Sentence: 'a crowd of people skiing and enjoying the snow'. Find frequency of the letter 'o'

Output: 5

Input: Consider Input: Sentence: 'a number of small boats on a beach near an umbrella'. Find frequency of the letter 's'

Output: 2

Input: Consider Input: Sentence: 'the room in the house is being remodeled'. Find frequency of the letter 'u'
Output: 1