import std.stdio, std.array, std.string, std.conv, std.algorithm; import std.typecons, std.range, std.random, std.math, std.container; import std.numeric, std.bigint, core.bitop, core.stdc.string; const long MOD = 10^^9 + 9; const long BASE = 31; void main() { auto S = readln.chomp; auto N = S.length.to!int; auto T = S.to!(dchar[]).reverse.to!string; if (is_kaibun(S)) { writeln(N-1); return; } auto P = new long[](N+1); auto P_INV = new long[](N+1); P[0] = P_INV[0] = 1; foreach (i; 0..N) P[i+1] = P[i] * BASE % MOD; foreach (i; 0..N) P_INV[i] = powmod(P[i], MOD-2, MOD); auto rh = new long[](N+1); rh[N] = 0; foreach (i; 0..N) rh[i+1] = (rh[i] + (S[i] - 'a') * P[i]) % MOD; auto hr = new long[](N+1); hr[N] = 0; foreach (i; 0..N) hr[i+1] = (hr[i] + (T[i] - 'a') * P[i]) % MOD; long hash_substr(int l, int r) { // [l, r] return ((rh[r+1] - rh[l]) * P_INV[l] % MOD + MOD) % MOD; } long hash_reverse(int l, int r) { int nl = N - r - 1; int nr = N - l - 1; return ((hr[nr+1] - hr[nl]) * P_INV[nl] % MOD + MOD) % MOD; } int bin_search(int r1, int l2) { if (r1 < 0 || l2 >= N) return -1; int hi = min(r1+1, N-l2); int lo = -1; while (hi - lo > 1) { int mid = (hi + lo) / 2; int l1 = r1 - mid; int r2 = l2 + mid; if (hash_substr(l1, r1) == hash_reverse(l2, r2)) lo = mid; else hi = mid; } return lo; } int ans = 0; foreach (i; 0..N) { // S[i]が中心 int len1 = bin_search(i-1, i+1) + 1; int r1 = i - len1 - 1; int l2 = i + len1 + 1; int len2 = max(bin_search(r1-1, l2), bin_search(r1, l2+1)) + 1; ans = max(ans, len1 * 2 + len2 * 2 + 1); } ans.writeln; } bool is_kaibun(string s) { return iota(s.length/2).map!(i => s[i] == s[s.length.to!int-i-1]).all; } long powmod(long a, long x, long m) { long ret = 1; while (x) { if (x % 2) ret = ret * a % m; a = a * a % m; x /= 2; } return ret; }