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

Ex Input:
Sentence: 'soccer players on opposite teams fight for control over a ball'. Find frequency of the letter 't'

Ex Output:
4


Ex Input:
Sentence: 'a bowl of vegetables in a soup like substance next to a spoon'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a traffic sign reads yellow on a clear day'. Find frequency of the letter 'a'

Ex Output:

6