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

Ex Input:
Sentence: 'a group of workers washing and cleaning fruits and vegetables'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'a tennis player after hitting a shot back to the other side of the court'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'two giraffes are walking, one on each side of the gate'. Find frequency of the letter 'o'

Ex Output:

4