#include <bits/stdc++.h>
#define MOD 1000000123
#define L 4000005
#define BASE 5
using namespace std;

string s;
map <char, int> let;
int n;
int v[L], h[L], v_rev[L], h_rev[L];

int qexp(int a, int b) {
  int p = 1;
  while (b) {
    if (b % 2 == 1)
      p = (1LL * p * a) % MOD;
    a = (1LL * a * a) % MOD;
    b /= 2;
  }
  return p;
}

int invMod(int x) {
  return qexp(x, MOD - 2);
}

int hashSeq(int i, int j) {
  return (1LL * (h[j] - h[i - 1] + MOD) * invMod(qexp(BASE, i))) % MOD;
}

int hashSeq_rev(int i, int j) {
  i = n - i + 1;
  j = n - j + 1;
  swap(i, j);
  return (1LL * (h_rev[j] - h_rev[i - 1] + MOD) * invMod(qexp(BASE, i))) % MOD;
}

void init() {
  let['A'] = 1;
  let['C'] = 2;
  let['G'] = 3;
  let['T'] = 4;
  n = s.size();
  for (int i = 0; i < n; i++)
    v[i + 1] = let[s[i]];
  for (int i = 1; i <= n; i++)
    h[i] = (1LL * h[i - 1] + 1LL * v[i] * qexp(BASE, i)) % MOD;
  for (int i = 1; i <= n; i++)
    v_rev[i] = v[n - i + 1];
  for (int i = 1; i <= n; i++)
    h_rev[i] = (1LL * h_rev[i - 1] + 1LL * v_rev[i] * qexp(BASE, i)) % MOD;
}

int main() {
  cin >> s;
  init();
  int anti = 1, antj = n;
  for (int i = 1; i <= n; i++)
    if (i + 1 + i - anti <= n && hashSeq(anti, i) == hashSeq_rev(i + 1, i + 1 + i - anti))
      anti = i + 1;
  for (int j = n; j > 0; j--)
    if (j - 1 - antj + j >= anti && hashSeq_rev(j, antj) == hashSeq(j - 1 - antj + j, j - 1))
      antj = j - 1;
  cout << antj - anti + 1 << "\n";
  return 0;
}