// includes {{{ #include<iostream> #include<iomanip> #include<algorithm> #include<vector> #include<stack> #include<queue> #include<deque> #include<map> #include<set> #include<tuple> #include<cmath> #include<random> #include<cassert> // }}} // #include<bits/stdc++.h> using namespace std; using ll = long long; int main() { std::ios::sync_with_stdio(false), std::cin.tie(0); string s; cin >> s; int n = s.size(); #define POS(x) cout<<((x)?"POSSIBLE":"IMPOSSIBLE")<<endl; #define Pos(x) cout<<((x)?"Possible":"Impossible")<<endl; #define YES(x) cout<<((x)?"YES":"NO")<<endl; #define Yes(x) cout<<((x)?"Yes":"No")<<endl; #define yes(x) cout<<((x)?"yes":"no")<<endl; YES(n%2 == 0 && (s.substr(n/2, n/2) == s.substr(0, n/2))); return 0; }