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

Input: Consider Input: Sentence: 'a plane with stairs next to it sitting in a large lot'. Find frequency of the letter 'i'

Output: 6

Input: Consider Input: Sentence: 'an elephant with broken tusks stands in front of a hill and boulders'. Find frequency of the letter 'n'

Output: 7

Input: Consider Input: Sentence: 'three giraffe and two zebras are grazing in the grass together'. Find frequency of the letter 'e'
Output: 8