#include <bits/stdc++.h> using namespace std; const int maxn = 105, baza = 29; const long long MOD = 998244353; int n; string s, s2; int dp[maxn][maxn]; long long poc, ans; string znak = "abcdefghijklmnopqrstuvwxyz"; int main (void){ ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); cin >> s; n = s.size(); s2 = s; for (int slovo = 0; slovo < 26; slovo++){ for (int pos = 0; pos < n; pos++){ s[pos] = znak[slovo]; poc = 0; for (int i = 0; i < n; i++){ for (int j = 0; j <= i; j++){ if (i == j) dp[i][j] = 1, poc++; else if (s[i] == s[j] and (i == j + 1 or dp[i - 1][j + 1] == 1)) dp[i][j] = 1, poc++; else dp[i][j] = 0; } } s = s2; ans = max(ans, poc); } } cout << ans << "\n"; return 0; }