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

Input: Consider Input: Sentence: 'a black cat laying down on a bed'. Find frequency of the letter 'y'

Output: 1


Input: Consider Input: Sentence: 'a bird in a tree looking up at branches'. Find frequency of the letter 'e'

Output: 3


Input: Consider Input: Sentence: 'the young zebra has it's head under neath the adult zebra'. Find frequency of the letter 'a'


Output: 6