#include <bits/stdc++.h>

using namespace std;

int main() {
  string s;
  cin >> s;
  auto r = s;
  reverse(r.begin(), r.end());
  const int n = s.size();
  set<string> st;
  for (int i = 0; i < n; ++i) {
    for (int j = 1; i + j <= n && j < n; ++j) st.insert(s.substr(i, j));
  }
  int res = 0;
  for (int i = 0; i < n; ++i) {
    for (int j = 1; i + j <= n && j < n; ++j) {
      if (st.count(r.substr(i, j))) res = max(res, j);
    }
  }
  cout << res << endl;
}