#include #include using namespace std; int main(){ string s; cin >> s; //cout << s.size() << endl; if(s.size() % 2 != 0) { cout << "NO" << endl; return 0; } string s1; for(int i = 0; i < s.size() / 2; i++){ s1 += s[i]; } string s2; for (int i = s.size() / 2; i < s.size(); i++){ s2 += s[i]; } //cout << s1 << " " << s2 << endl; if(s1 == s2){ cout << "YES" << endl; }else{ cout << "NO" << endl; } }