#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* macro */ #define rep(i, a, n) for (int i = (int)(a); i < (int)(n); i++) #define rrep(i, a, n) for (int i = ((int)(n - 1)); i >= (int)(a); i--) #define Rep(i, a, n) for (i64 i = (i64)(a); i < (i64)(n); i++) #define RRep(i, a, n) for (i64 i = ((i64)(n - i64(1))); i >= (i64)(a); i--) #define all(v) (v).begin(), (v).end() #define rall(v) (v).rbegin(), (v).rend() #define Bit(n) (1LL << (n)) /* macro end */ /* template */ namespace ebi { #ifdef LOCAL #define debug(...) \ std::cerr << "LINE: " << __LINE__ << " [" << #__VA_ARGS__ << "]:", \ debug_out(__VA_ARGS__) #else #define debug(...) #endif void debug_out() { std::cerr << std::endl; } template void debug_out(Head h, Tail... t) { std::cerr << " " << h; if (sizeof...(t) > 0) std::cout << " :"; debug_out(t...); } template std::ostream &operator<<(std::ostream &os, const std::pair &pa) { return os << pa.first << " " << pa.second; } template std::istream &operator>>(std::istream &os, std::pair &pa) { return os >> pa.first >> pa.second; } template std::ostream &operator<<(std::ostream &os, const std::vector &vec) { for (std::size_t i = 0; i < vec.size(); i++) os << vec[i] << (i + 1 == vec.size() ? "" : " "); return os; } template std::istream &operator>>(std::istream &os, std::vector &vec) { for (T &e : vec) std::cin >> e; return os; } template std::ostream &operator<<(std::ostream &os, const std::optional &opt) { if (opt) { os << opt.value(); } else { os << "invalid value"; } return os; } using std::size_t; using i32 = std::int32_t; using u32 = std::uint32_t; using i64 = std::int64_t; using u64 = std::uint64_t; template auto make_vector(int n) { return std::vector(n, init); } template auto make_vector(Head n, Tail... ts) { return std::vector(n, make_vector(ts...)); } template inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; } template T pow(T x, i64 n) { T res = 1; while (n > 0) { if (n & 1) res = res * x; x = x * x; n >>= 1; } return res; } template T mod_pow(T x, i64 n, i64 mod) { T res = 1; while (n > 0) { if (n & 1) res = (res * x) % mod; x = (x * x) % mod; n >>= 1; } return res; } template T scan() { T val; std::cin >> val; return val; } template struct Edge { int to; T cost; Edge(int _to, T _cost = 1) : to(_to), cost(_cost) {} }; template struct Graph : std::vector>> { using std::vector>>::vector; void add_edge(int u, int v, T w, bool directed = false) { (*this)[u].emplace_back(v, w); if (directed) return; (*this)[v].emplace_back(u, w); } }; struct graph : std::vector> { using std::vector>::vector; void add_edge(int u, int v, bool directed = false) { (*this)[u].emplace_back(v); if (directed) return; (*this)[v].emplace_back(u); } }; constexpr i64 LNF = std::numeric_limits::max() / 4; constexpr int INF = std::numeric_limits::max() / 2; const std::vector dy = {1, 0, -1, 0, 1, 1, -1, -1}; const std::vector dx = {0, 1, 0, -1, 1, -1, 1, -1}; } // namespace ebi namespace ebi { void main_() { std::string s; std::cin >> s; int n = s.size(); std::vector nxt(n, std::vector()); rep(i,0,n) { rep(j,0,n) { if(i-j < 0 || i+j >= n) break; if(s[i-j] == s[i+j]) { nxt[i-j].emplace_back(2*j+1); } else { break; } } rep(j,0,n) { if(i - j < 0 || i+j+1 >= n) break; if(s[i-j] == s[i+j+1]) { nxt[i-j].emplace_back(2*(j+1)); } else { break; } } } std::vector dp(n+1, -1); dp[0] = INF; rep(i,0,n) { for(auto nv: nxt[i]) { assert(i+nv <= n); chmax(dp[i+nv], std::min(dp[i], nv)); } } std::cout << dp[n] << '\n'; } } // namespace ebi int main() { std::cout << std::fixed << std::setprecision(15); std::cin.tie(nullptr); std::ios::sync_with_stdio(false); int t = 1; // std::cin >> t; while (t--) { ebi::main_(); } return 0; }