난이도: Medium 문제 설명You are given a string s.You can perform the following process on s any number of times:Choose an index i in the string such that there is at least one character to the left of index i that is equal to s[i], and at least one character to the right that is also equal to s[i].Delete the closest character to the left of index i that is equal to s[i].Delete the closest character to ..