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

Input: Consider Input: Sentence: 'an image of a cautionary construction sign'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'a chair and umbrella on a sandy beach'. Find frequency of the letter 's'

Output: 1


Input: Consider Input: Sentence: 'two giraffes, one large one child size are standing in front of some artificial looking rocks'. Find frequency of the letter 'a'


Output: 6