#include <bits/stdc++.h> using namespace std; const int maxn = 100005, baza = 29; const long long MOD = 1e9+7; int n; string s; int dn1[maxn], dp1[maxn], dn2[maxn], dp2[maxn]; int h[maxn], hr[maxn], mn[maxn]; long long smanji[maxn], povecaj[baza][maxn]; vector <int> dodajl[maxn], dodajr[maxn], maknil[maxn], maknir[maxn]; long long sumal, sumar, ukpl, ukpr, ans, poc; int add (int x, int y){ if (x + y >= MOD) return x + y - MOD; if (x + y < 0) return x + y + MOD; return x + y; } long long umn (long long x, long long y){ return (x * y) % MOD; } int ha (int x, int y){ if (x == 0) return umn(h[y], mn[n - 1 - y]); else return umn(h[y] - h[x - 1], mn[n - 1 - y]); } int har (int x, int y){ if (y == n - 1) return umn(hr[x], mn[x]); else return umn(hr[x] - hr[y + 1], mn[x]); } int main (void){ ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); cin >> s; n = s.size(); h[0] = s[0] - 'a' + 1; mn[0] = 1; for (int i = 1; i < n; i++){ mn[i] = umn(mn[i - 1], baza); h[i] = add(h[i - 1], umn((s[i] - 'a' + 1), mn[i])); } hr[n - 1] = s[n - 1] - 'a' + 1; for (int i = n - 2; i >= 0; i--){ hr[i] = add(hr[i + 1], umn((s[i] - 'a' + 1), mn[n - i - 1])); } for (int i = 0; i < n; i++){ int low = 0, high = min(i, n - 1 - i), mid; while (low < high){ mid = (low + high) / 2 + 1; if (ha(i - mid, i - 1) == har(i + 1, i + mid)) low = mid; else high = mid - 1; } dn1[i] = low; low = 0, high = min(i - dn1[i] - 1, n - 2 - (dn1[i] + i)); while (low < high){ mid = (low + high) / 2 + 1; if (ha(i - dn1[i] - 1 - mid, i - dn1[i] - 2) == har(i + dn1[i] + 2, i + dn1[i] + 1 + mid)) low = mid; else high = mid - 1; } dn2[i] = low; poc += dn1[i]; } for (int i = 0; i < n - 1; i++){ int low = 0, high = min(i + 1, n - 1 - i), mid; while (low < high){ mid = (low + high) / 2 + 1; if (ha(i - mid + 1, i) == ha(i + 1, i + mid)) low = mid; else high = mid - 1; } dp1[i] = low; poc += dp1[i]; low = 0, high = min(i - dp1[i], n - 2 - (dp1[i] + i)); while (low < high){ mid = (low + high) / 2 + 1; if (ha(i - dp1[i] - mid, i - dp1[i] - 1) == ha(i + dp1[i] + 2, i + dp1[i] + 1 + mid)) low = mid; else high = mid - 1; } dp2[i] = low; } poc += n; for (int i = 0; i < n; i++){ dodajl[i - dn1[i]].push_back(i); maknil[i].push_back(i); dodajr[i + 1].push_back(i); maknir[i + 1 + dn1[i]].push_back(i); } for (int i = 0; i < n; i++){ for (int j = 0; j < dodajl[i].size(); j++){ int c = dodajl[i][j]; sumal += dn1[c] - c + 1; ukpl++; } for (int j = 0; j < maknil[i].size(); j++){ int c = maknil[i][j]; sumal -= dn1[c] - c + 1; ukpl--; } for (int j = 0; j < dodajr[i].size(); j++){ int c = dodajr[i][j]; sumar += dn1[c] + c + 1; ukpr++; } for (int j = 0; j < maknir[i].size(); j++){ int c = maknir[i][j]; sumar -= dn1[c] + c + 1; ukpr--; } smanji[i] = sumal + sumar + ukpl * i - ukpr * i; povecaj[s[i] - 'a'][i] += sumal + sumar + ukpl * i - ukpr * i; } for (int i = 0; i < n; i++){ dodajl[i].clear(); maknil[i].clear(); dodajr[i].clear(); maknir[i].clear(); } for (int i = 0; i < n - 1; i++){ if (dp1[i] != 0){ dodajl[i - dp1[i] + 1].push_back(i); maknil[i + 1].push_back(i); dodajr[i + 1].push_back(i); maknir[i + dp1[i] + 1].push_back(i); } } sumal = 0, sumar = 0, ukpl = 0, ukpr = 0; for (int i = 0; i < n; i++){ for (int j = 0; j < dodajl[i].size(); j++){ int c = dodajl[i][j]; sumal += dp1[c] - c ; ukpl++; } for (int j = 0; j < maknil[i].size(); j++){ int c = maknil[i][j]; sumal -= dp1[c] - c; ukpl--; } for (int j = 0; j < dodajr[i].size(); j++){ int c = dodajr[i][j]; sumar += dp1[c] + c + 1; ukpr++; } for (int j = 0; j < maknir[i].size(); j++){ int c = maknir[i][j]; sumar -= dp1[c] + c + 1; ukpr--; } //cout << smanji[i] << " "; smanji[i] += sumal + sumar + ukpl * i - ukpr * i; povecaj[s[i] - 'a'][i] += sumal + sumar + ukpl * i - ukpr * i; //cout << smanji[i] << endl; } for (int slovo = 0; slovo < 26; slovo++){ for (int i = 0; i < n; i++){ if (i + dn1[i] < n - 1 and i - dn1[i] > 0 and s[i + dn1[i] + 1] - 'a' == slovo) povecaj[slovo][i - dn1[i] - 1] += dn2[i] + 1; if (i + dn1[i] < n - 1 and i - dn1[i] > 0 and s[i - dn1[i] - 1] - 'a' == slovo) povecaj[slovo][i + dn1[i] + 1] += dn2[i] + 1; } for (int i = 0; i < n - 1; i++){ if (i + dp1[i] < n - 1 and i - dp1[i] + 1 > 0 and s[i + dp1[i] + 1] - 'a' == slovo) povecaj[slovo][i - dp1[i]] += dp2[i] + 1; if (i + dp1[i] < n - 1 and i - dp1[i] + 1 > 0 and s[i - dp1[i]] - 'a' == slovo) povecaj[slovo][i + dp1[i] + 1] += dp2[i] + 1; } } ans = poc; //cout << poc << endl; for (int i = 0; i < n; i++){ long long maxi = 0; for (int slovo = 0; slovo < 26; slovo++) maxi = max(maxi, povecaj[slovo][i]); ans = max(ans, poc + maxi - smanji[i]); //cout << smanji[i] << " " << maxi << endl; } cout << ans << "\n"; return 0; }