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

Ex Input:
Sentence: 'a traffic signal by a wire filled with some birds'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'people playing wii bowling in a modern library'. Find frequency of the letter 'o'

Ex Output:
3


Ex Input:
Sentence: 'a steamer filled with different types of vegetables'. Find frequency of the letter 'i'

Ex Output:

3