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

Input: Consider Input: Sentence: 'a red and white train passing a train station'. Find frequency of the letter 'a'

Output: 7


Input: Consider Input: Sentence: 'a big bear walks through some grass'. Find frequency of the letter 'a'

Output: 4


Input: Consider Input: Sentence: 'wooden pole in sub urban area with intersection and trees nearby'. Find frequency of the letter 'n'


Output: 7