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

Ex Input:
Sentence: 'the little girl is flying her kite in the field'. Find frequency of the letter 'i'

Ex Output:
7


Ex Input:
Sentence: 'a young man with glasses on is taking a big bite'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'black and white image of a man in bed with two dogs'. Find frequency of the letter 'n'

Ex Output:

3