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

Ex Input:
Sentence: 'hotel towels with sunglasses perched and hotel business cards and catalog'. Find frequency of the letter 'o'

Ex Output:
4


Ex Input:
Sentence: 'a railroad train pulling up to the train platform'. Find frequency of the letter 'o'

Ex Output:
3


Ex Input:
Sentence: 'a man riding a board on top of a wave'. Find frequency of the letter 'o'

Ex Output:

4