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

Ex Input:
Sentence: 'a woman is taking a sip of a drink from a glass'. Find frequency of the letter 'i'

Ex Output:
4


Ex Input:
Sentence: 'a glass vase sits between two statues'. Find frequency of the letter 'o'

Ex Output:
1


Ex Input:
Sentence: 'a bathroom with toilet glass sink, mirror and extra toilet paper'. Find frequency of the letter 't'

Ex Output:

7