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

Input: Consider Input: Sentence: 'two people under an umbrella while walking down a sidewalk'. Find frequency of the letter 'i'

Output: 3


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: 'a child in a red shirt eating a hot dog'. Find frequency of the letter 'a'


Output: 4