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

Ex Input:
Sentence: 'a snowboarder making a jump of a snowy ledge'. Find frequency of the letter 'o'

Ex Output:
4


Ex Input:
Sentence: 'a bird on a tree is flapping its wings'. Find frequency of the letter 'o'

Ex Output:
1


Ex Input:
Sentence: 'a cat peeks out of a green bag'. Find frequency of the letter 'b'

Ex Output:

1