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

Ex Input:
Sentence: 'a group of people are playing soccer on a beach'. Find frequency of the letter 'l'

Ex Output:
2


Ex Input:
Sentence: 'four women around a man sitting in front of a cake'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'one penguin playing in a pool of water while three other penguins watch'. Find frequency of the letter 'l'

Ex Output:

3