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

Input: Consider Input: Sentence: 'a red and white train passing a train station'. Find frequency of the letter 'a'

Output: 7


Input: Consider Input: Sentence: 'a man in a black wet suit rides an orange surfboard on the water'. Find frequency of the letter 'o'

Output: 3


Input: Consider Input: Sentence: 'the cat is laying on top of the television in the room'. Find frequency of the letter 'i'


Output: 5