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

Ex Input:
Sentence: 'cars parked outside if a retail store'. Find frequency of the letter 'd'

Ex Output:
2


Ex Input:
Sentence: 'a group of people standing around a table filled with assorted electronic devices'. Find frequency of the letter 'w'

Ex Output:
1


Ex Input:
Sentence: 'a snowboarder jumps into the air while traveling down a mountain at twilight'. Find frequency of the letter 'i'

Ex Output:

7