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

Input: Consider Input: Sentence: 'a man and a woman are walking down the street with an umbrella over their heads'. Find frequency of the letter 'w'

Output: 4


Input: Consider Input: Sentence: 'a toilet sits in a cluttered bathroom next to a sink'. Find frequency of the letter 'a'

Output: 4


Input: Consider Input: Sentence: 'five snowboarders doing tricks on the snowboard course'. Find frequency of the letter 'n'


Output: 4