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

Ex Input:
Sentence: 'people playing wii bowling in a modern library'. Find frequency of the letter 'o'

Ex Output:
3


Ex Input:
Sentence: 'three young people goofing around; one of the guys has a football, the girl has a teddy bear'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'the lobby of the building has a large fountain with umbrellas above it'. Find frequency of the letter 'u'

Ex Output:

3