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

Input: Consider Input: Sentence: 'a picture of two men on a motorcycle in front of a railroad track'. Find frequency of the letter 'n'

Output: 4


Input: Consider Input: Sentence: 'a surfer wipes out on a huge wave'. Find frequency of the letter 'a'

Output: 3


Input: Consider Input: Sentence: 'an orange cat sitting on the ground next to a  purse'. Find frequency of the letter 's'


Output: 2