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

Ex Input:
Sentence: 'three woman are having a discussion in the kitchen'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'a herd of zebra standing on top  of a grass covered field'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a bus terminal with several buses and three people waiting'. Find frequency of the letter 'g'

Ex Output:

1