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

Ex Input:
Sentence: 'a man standing in front of a statue near a metal pole'. Find frequency of the letter 'f'

Ex Output:
2


Ex Input:
Sentence: 'a dilapidated bench in a park under a tree'. Find frequency of the letter 'p'

Ex Output:
2


Ex Input:
Sentence: 'field of zebra's eating grass, and drinking water'. Find frequency of the letter 's'

Ex Output:

3