#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++;
}
}
s = s2;
ans = max(ans, poc);
}
}
cout << ans << "\n";
return 0;
}
