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 sidewalk jumping with an umbrella'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'a boy that is sitting at a table with pizza'. Find frequency of the letter 's'

Output: 2


Input: Consider Input: Sentence: 'a cake is designed with a train theme'. Find frequency of the letter 'r'


Output: 1