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

Input: Consider Input: Sentence: 'a log in the water with three birds perched on it'. Find frequency of the letter 'r'

Output: 4


Input: Consider Input: Sentence: 'a man standing on a tennis court holding a racquet'. Find frequency of the letter 's'

Output: 2


Input: Consider Input: Sentence: 'a man is sitting at a desk with a desktop computer on it while he uses a laptop'. Find frequency of the letter 'i'


Output: 6