class Solution {
    public String removeDuplicates(String s) {
        StringBuilder res=new StringBuilder();
        Stack<Character> stack=new Stack<>();
        char[] letters=s.toCharArray();
        
        for(int i=letters.length-1; i>=0; i--){
            if(!stack.isEmpty()&&letters[i]==stack.peek())
                stack.pop();
            else
                stack.push(letters[i]);
        }
        
        while(!stack.isEmpty()){
            res.append(stack.pop());
        }
        
        return res.toString();
    }
}