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

Input: Consider Input: Sentence: 'group of snowboarders on a snowy trail overlooking a mountain'. Find frequency of the letter 'r'

Output: 5


Input: Consider Input: Sentence: 'a dog laying on the back of a boat in the water'. Find frequency of the letter 't'

Output: 4


Input: Consider Input: Sentence: 'a boat sails across the water in an area with many trees and mountains'. Find frequency of the letter 'n'


Output: 6