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 of boys in a field playing baseball'. Find frequency of the letter 'i'

Output: 3


Input: Consider Input: Sentence: 'two boys are doing skateboard jumps in the street'. Find frequency of the letter 's'

Output: 4


Input: Consider Input: Sentence: 'a girl is standing with a horse in an arena'. Find frequency of the letter 'a'


Output: 6