#pragma region Macros #include using namespace std; template inline bool chmax(T &a, T b) { if(a < b) { a = b; return 1; } return 0; } template inline bool chmin(T &a, T b) { if(a > b) { a = b; return 1; } return 0; } #ifdef DEBUG template ostream &operator<<(ostream &os, const pair &p) { os << '(' << p.first << ',' << p.second << ')'; return os; } template ostream &operator<<(ostream &os, const vector &v) { os << '{'; for(int i = 0; i < (int)v.size(); i++) { if(i) { os << ','; } os << v[i]; } os << '}'; return os; } void debugg() { cerr << endl; } template void debugg(const T &x, const Args &... args) { cerr << " " << x; debugg(args...); } #define debug(...) \ cerr << __LINE__ << " [" << #__VA_ARGS__ << "]: ", debugg(__VA_ARGS__) #define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl #else #define debug(...) (void(0)) #define dump(x) (void(0)) #endif struct Setup { Setup() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } __Setup; using ll = long long; #define ALL(v) (v).begin(), (v).end() #define RALL(v) (v).rbegin(), (v).rend() #define FOR(i, a, b) for(int i = (a); i < int(b); i++) #define REP(i, n) FOR(i, 0, n) const int INF = 1 << 30; const ll LLINF = 1LL << 60; constexpr int MOD = 1000000007; const int dx[4] = {1, 0, -1, 0}; const int dy[4] = {0, 1, 0, -1}; void Case(int i) { cout << "Case #" << i << ": "; } int popcount(int x) { return __builtin_popcount(x); } ll popcount(ll x) { return __builtin_popcountll(x); } #pragma endregion Macros int main() { string s; cin >> s; int len = s.size(); bool f = true; { char c = s[0]; FOR(i, 1, len) if(s[i] != c) { f = false; break; } } if(len == 3 and s[0] == s[2] and s[0] != s[1]) { cout << -1 << endl; return 0; } if(f) { cout << (len % 2 ? -1 : 0) << endl; return 0; } string t = s; reverse(ALL(t)); if(s == t) { cout << len-2 << endl; } else { cout << len << endl; } }