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

Input: Consider Input: Sentence: 'three young children playing with a ball in front of a huge bridge'. Find frequency of the letter 'e'

Output: 5


Input: Consider Input: Sentence: 'a man in a black wet suit rides an orange surfboard on the water'. Find frequency of the letter 'o'

Output: 3


Input: Consider Input: Sentence: 'a little baby sitting next to a small dog and a piece of luggage'. Find frequency of the letter 'a'


Output: 7