#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #if __has_include() #include using namespace atcoder; #endif #define GET_MACRO(_1, _2, _3, NAME, ...) NAME #define _rep(i, n) _rep2(i, 0, n) #define _rep2(i, a, b) for(int i = (int)(a); i < (int)(b); i++) #define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__) #define all(x) (x).begin(), (x).end() #define rall(x) (x).rbegin(), (x).rend() using i64 = long long; template bool chmin(T& a, const U& b) { return (b < a) ? (a = b, true) : false; } template bool chmax(T& a, const U& b) { return (b > a) ? (a = b, true) : false; } templateistream& operator>>(istream&i,vector&v){rep(j,v.size())i>>v[j];return i;} templatestring join(vector&v){stringstream s;rep(i,v.size())s<<' '<ostream& operator<<(ostream&o,vector&v){if(v.size())o<string join(vector>&vv){string s="\n";rep(i,vv.size())s+=join(vv[i])+"\n";return s;} templateostream& operator<<(ostream&o,vector>&vv){if(vv.size())o< using pq = priority_queue, greater>; int main() { string s; cin >> s; int n = s.size(); set sc; for(auto i : s) sc.insert(i); if(sc.size() == 1) { if(n & 1) cout << -1 << endl; else cout << 0 << endl; } else { auto t = s; reverse(all(t)); if(s != t) cout << n << endl; else if(n != 3) cout << n - 2 << endl; else cout << -1 << endl; } return 0; }