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

Input: Consider Input: Sentence: 'a train is sitting at a train station'. Find frequency of the letter 'r'

Output: 2


Input: Consider Input: Sentence: 'a bowl of vegetables in a soup like substance next to a spoon'. Find frequency of the letter 'a'

Output: 5


Input: Consider Input: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'


Output: 1