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

Input: Consider Input: Sentence: 'a person riding a skate board on a city street'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'a sailboat is floating near the rocky shore of a beach'. Find frequency of the letter 'o'

Output: 5


Input: Consider Input: Sentence: 'a man posing wearing a nice suit and looking up at the camera'. Find frequency of the letter 'i'


Output: 5