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

Ex Input:
Sentence: 'pedestrian in stripe clothing standing on street corner'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'two men in black wet suits beside a white surfboard'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'book about vegetables surrounded by fresh fruits and vegetables'. Find frequency of the letter 'e'

Ex Output:

8