Subarrays with distinct integers!

Given an array A of positive integers,call a (contiguous,not necessarily distinct) subarray of A good if the number of different integers in that subarray is exactly B.

(For example: [1, 2, 3, 1, 2] has 3 different integers 1, 2 and 3)

Return the number of good subarrays of A.

1 <= |A| <= 40000

1 <= A[i] <= |A|

1 <= B <= |A|

The first argument given is the integer array A.

The second argument given is an integer B.

Return an integer denoting the number of good subarrays of A.

Input 1:

 A = [1, 2, 1, 2, 3]
 B = 2

Input 2:

 A = [1, 2, 1, 3, 4]
 B = 3

Output 1:

 7

Output 2:

 3

Explanation 1:

  Subarrays formed with exactly 2 different integers: [1, 2], [2, 1], [1, 2], [2, 3], [1, 2, 1], [2, 1, 2], [1, 2, 1, 2].

Explanation 2:

  Subarrays formed with exactly 3 different integers: [1, 2, 1, 3], [2, 1, 3], [1, 3, 4].