a string s nice letter alphabet s contain appear uppercase lowercase for example ababb nice a appear B b appear however aba b appear b notgiven string s return long substre s nice if multiple return substre early occurrence if return stre Example 1input s YazaAayOutput aaaexplanation aaa nice string Aa letter alphabet s a appearaaa long nice substringExample 2input s BbOutput BbExplanation Bb nice string b b appear the string substringExample 3input s cOutput Explanation there nice substring Constraints1 slength 100s consist uppercase lowercase english letter