class Solution {
    public String makeGood(String s) {
        Stack<Character> stack = new Stack();
        for(char ch: s.toCharArray()){
            if(!stack.isEmpty() && Math.abs(stack.peek()-ch) == 32)
                stack.pop();
            else
                stack.push(ch);
        }
        
        char temp[] = new char[stack.size()];
        int n = stack.size()-1;
        while(!stack.isEmpty()){
            temp[n--] = stack.pop();
        }
        
        return new String(temp);
    }
}