# AMZ (Geek for geek)
"""
    Count all possible substrings that has exactly k distinct char.

    Example 1
    Input: abc, k = 2
    Output:2
    Possible substrings are {"ab", ""}

    Example 2
    "aba" k = 2

    3
    "aa" k = 1
    Output: "a", "a", "aa"

    4
    "abcaaaab" k = 3

    5 edge case **
    "abcbaa" k = 3
"""

class Solution():
    def Substrings_with_K_distinct(self, S):
        pass