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

Input: Consider Input: Sentence: 'an airplane is being towed away from the jet bridge'. Find frequency of the letter 's'

Output: 1


Input: Consider Input: Sentence: 'a couple of items that are on the wall'. Find frequency of the letter 'm'

Output: 1


Input: Consider Input: Sentence: 'a group of people speak to a female surfer on the beach'. Find frequency of the letter 'p'


Output: 4