#include <iostream>
#include <string>
using namespace std;
    
int main()
{
    string a = "abbaca";
    int i = 0;
    while (i < a.size()){
        if (a[i] == a[i+1]){
            a.erase(i, 2);
            i = 0;
        }
        else{
            i++;
        }
    }
    cout << a;
    
    return 0;
}