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

Input: Consider Input: Sentence: 'two giraffes standing next to some trees'. Find frequency of the letter 'f'

Output: 2

Input: Consider Input: Sentence: 'a couple of boys in a field playing baseball'. Find frequency of the letter 'i'

Output: 3

Input: Consider Input: Sentence: 'people are loading the top of a bus and other people are standing around watching'. Find frequency of the letter 's'
Output: 2