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

Ex Input:
Sentence: 'an old woman is holding her cat in front of a camera'. Find frequency of the letter 'r'

Ex Output:
3


Ex Input:
Sentence: 'two little girls playing with a bat and a tennis ball'. Find frequency of the letter 'w'

Ex Output:
2


Ex Input:
Sentence: 'a lady sitting in a very big wooden chair'. Find frequency of the letter 'y'

Ex Output:

2