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 on a skateboard going down a ramp'. Find frequency of the letter 'n'

Output: 4


Input: Consider Input: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'

Output: 1


Input: Consider Input: Sentence: 'a locomotive train resting on some tracks next to a building'. Find frequency of the letter 's'


Output: 3