****No string methods or any user-defined modules***

Example 1	Example 2	Example 3	Example 4
actxaxu 5 actxa abcafaghu 4 acaf sfucmptsfu 8 sfucmpts quit	quit	hello hello 3 hel quit	yumghhs 6 yumghh quit

SubstringFinder1 works as follows:

Takes a string called source as the first input.

Takes a positive integer k as the second input. SubstringFinder1 assumes the user provides a number greater than zero.

SubstringFinder1 does the processing and prints the k-length substring of source with the greatest number of unique characters.

If there are multiple substrings that satisfy the condition in the previous step, SubstringFinder1 prints the one that appears first in the user-provided string, source.

SubstringFinder1 continues to get inputs from the user until the user enters 'quit' for string source.

You are not allowed to use any Python built-in methods or user-defined modules in developing SubstringFinder1. You can see examples of SubstringFinder1 input and output in the table above.Note that your program input and output format should be exactly the same as the format of the examples shown in the table above

****No string methods or any user-defined modules***