#include<bits/stdc++.h>
using namespace std;

// } Driver Code Ends
class Solution {
  public:
    // Remove all the consecutive duplicate pairs and concatenate the
    // remaining string to replace the original string. This operation
    // can be applied any number of times    
    string removePair(string s) {
        // code here
        string output;
        size_t i = 1;        
        for (auto c: s)
        {
            if (output.size() && output.back() == c)
                output.pop_back();
            else
                output.push_back(c);

            cout << s.substr(0, i++) << " output: " << output << endl;
        }
        
        return output.size() ? output : "-1";        
    }
};

int main() {
    Solution obj;
    vector<tuple<string,string>> v = {
        {"aaabbaaccd", "ad"},
        // Remove (aa)abbaaccd => abbaaccd
        // Remove a(bb)aaccd => aaaccd
        // Remove (aa)accd => accd
        // Remove a(cc)d => ad
        {"xiiccccssxxxgggww", "g"}
        // Remove x(ii)ccccssxxxgggww => xccccssxxxgggww
        // Remove x(cc)ccssxxxgggww => xccssxxxgggww
        // Remove x(cc)ssxxxgggww => xssxxxgggww
        // Remove x(ss)xxxgggww => xxxxgggww
        // Remove (xx)xxgggww => xxgggww
        // Remove (xx)gggww => gggww
        // Remove (gg)gww => gww
        // Remove g(ww) => g
    };

    for (auto i: v)
    {
        string res = obj.removePair(get<0>(i));
        cout << res       << endl;
        cout << get<1>(i) << endl;
        cout << "------------" << endl;
    }
}

// } Driver Code Ends