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

Input: Consider Input: Sentence: 'a notebook and pen are left on a park bench'. Find frequency of the letter 'e'

Output: 5


Input: Consider Input: Sentence: 'a dog is shown sitting on rocks by the beach'. Find frequency of the letter 'a'

Output: 2


Input: Consider Input: Sentence: 'a military fighter jet in flight armed with missiles'. Find frequency of the letter 'f'


Output: 2