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

Input: Consider Input: Sentence: 'a herd of zebra standing on top  of a grass covered field'. Find frequency of the letter 'e'

Output: 5


Input: Consider Input: Sentence: 'four women around a man sitting in front of a cake'. Find frequency of the letter 'o'

Output: 5


Input: Consider Input: Sentence: 'the monitor and shelves are big enough for all the workers to use'. Find frequency of the letter 't'


Output: 4