python

A string is called balanced when every letter occurring in the string, appears both in upper- and lowercase. For example, the string "CATattac" is balanced ('a', 'c' and 't'occur in both cases), but "Madam" is not ('d' and 'a' appear only in lowercase). Note that the number of occurrences does not matter. Write a function: def solution(s) that, given a string S of length N, returns the length of the shortest balanced fragment of S. If S does not contain any balanced fragments, the function should return -1. Examples: 1. Given S = "ZABaabza", the function should return 5. The shortest balanced fragment of S is "ABaab". 2. Given S = "TacoCat", the function should return -1. There is no balanced fragment. 3. Given S = "AcZCbaBz", the function should return 8. The shortest balanced fragment is the whole string. 4. Given S = "abcdefghijklmnopqrstuvwxyz", the function should return -1. Assume that: Nis an integer within the range [1..200); string S consists only of letters ('a'-'z' and/or 'A'-'Z')