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

Input: Consider Input: Sentence: 'a small boat and a large boat on a river near a city'. Find frequency of the letter 'a'

Output: 10


Input: Consider Input: Sentence: 'a person is water skiing and there are birds flying around above them'. Find frequency of the letter 'n'

Output: 5


Input: Consider Input: Sentence: 'a family of zebras in an open landscape'. Find frequency of the letter 'a'


Output: 6