class Solution {
    public String removeDuplicates(String s) {
        Stack<Character> stack = new Stack<>();
        for (int i =0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (!stack.isEmpty() && stack.peek() == c) {
                while(i + 1< s.length() && s.charAt(i+1) == c) i++;
                stack.pop();
                continue;
            } else {
                stack.push(c);
            }
        }
        StringBuilder sb = new StringBuilder();
        for (char c : stack) {
            sb.append(c);
        }
        return sb.toString();
    }
}