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

Ex Input:
Sentence: 'a very big nice looking living room with nice furnishings'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a man opening up a package sitting on a couch'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'people on a long bridge walking in the rain with umbrellas'. Find frequency of the letter 'u'

Ex Output:

1