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

Ex Input:
Sentence: 'a train is sitting at a train station'. Find frequency of the letter 'r'

Ex Output:
2


Ex Input:
Sentence: 'red chair next to side table with lamp in residential home'. Find frequency of the letter 'm'

Ex Output:
2


Ex Input:
Sentence: 'the two men play a frisbee game in the field'. Find frequency of the letter 'm'

Ex Output:

2