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

Ex Input:
Sentence: 'a green bus driving in a street filled with heavy traffic'. Find frequency of the letter 'v'

Ex Output:
2


Ex Input:
Sentence: 'the child is waving a small flag as she stands near two women'. Find frequency of the letter 'g'

Ex Output:
2


Ex Input:
Sentence: 'two cows grazing under a rising full moon'. Find frequency of the letter 'm'

Ex Output:

1