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

Input: Consider Input: Sentence: 'a man opening up a package sitting on a couch'. Find frequency of the letter 'n'

Output: 5


Input: Consider Input: Sentence: 'a person working at an airport, outside of an airplane'. Find frequency of the letter 'r'

Output: 5


Input: Consider Input: Sentence: 'a group of men slicing into a large celebratory cake'. Find frequency of the letter 'a'


Output: 5