#include <bits/stdc++.h> using namespace std; int main() { string s; cin>>s; stack<char> a; int n=s.size(); for(int i=0;i<n;i++) { if((!a.empty())&&a.top()==s[i]) a.pop(); else a.push(s[i]); } if(a.empty()) cout<<0; else { string ss; while(!a.empty()) { ss.push_back(a.top()); a.pop(); } reverse(ss.begin(),ss.end()); cout<<ss; } return 0; }