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: 'pedestrians pass by a stop sign, some holding surfboards'. Find frequency of the letter 'n'

Output: 3


Input: Consider Input: Sentence: 'a child in a red coat walking towards a red boat'. Find frequency of the letter 'a'


Output: 7