#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  string s;
  cin >> s;
  int ans = 1;
  for (int l = 0; l < s.size(); ++l) {
    for (int r = l + 1; r < s.size(); ++r) {
      int len = r - l + 1;
      int cnt = 0;
      for (int i = 0; i < len / 2; ++i)
        if (s[l + i] != s[r - i]) ++cnt;
      ans = max(ans, len - 2 * cnt);
    }
  }
  cout << ans << '\n';
  return 0;
}