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 group of men standing on the side of a boat'. Find frequency of the letter 'o'

Output: 5


Input: Consider Input: Sentence: 'an old fashioned refrigerator  with condiments on the door'. Find frequency of the letter 'a'


Output: 3