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

Input: Consider Input: Sentence: 'a couple is cutting in to a cake at a wedding'. Find frequency of the letter 'd'

Output: 2

Input: Consider Input: Sentence: 'the two dogs are playing in the pen together'. Find frequency of the letter 'o'

Output: 3

Input: Consider Input: Sentence: 'a person jumping a dirt bike in the air'. Find frequency of the letter 'i'
Output: 5