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

Input: Consider Input: Sentence: 'a yellow fire hydrant in the forefront of a roadway'. Find frequency of the letter 'r'

Output: 5


Input: Consider Input: Sentence: 'a truck with a camper sits parked in some vegetation'. Find frequency of the letter 's'

Output: 3


Input: Consider Input: Sentence: 'a black and white photo of a train at a station'. Find frequency of the letter 'a'


Output: 8