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

Ex Input:
Sentence: 'there is an old stove with old pots on the burners'. Find frequency of the letter 't'

Ex Output:
5


Ex Input:
Sentence: 'a toilet of some sort near a sink of some sort'. Find frequency of the letter 'o'

Ex Output:
7


Ex Input:
Sentence: 'boy skateboarding next to a graffitti covered wall'. Find frequency of the letter 'g'

Ex Output:

2