#include <iostream>
#include <vector>
#include <string>

using namespace std;

int main() {
  string S;
  cin >> S;

  int N = S.size();
  vector<pair<char, int>> buckets;
  for (int i = 0; i < N; i++) {
    int j = i + 1;
    while (j < N && S[i] == S[j]) {
      j++;
    }
    buckets.emplace_back(S[i], j - i);
    i = j - 1;
  }

  if (buckets.size() % 2 == 0) {
    cout << 0 << "\n";
    return 0;
  }

  int M = buckets.size();
  if (buckets[M / 2].second == 1) {
    cout << 0 << "\n";
    return 0;
  }

  // cerr << buckets.size() << "\n";
  // for (const auto& [x, y] : buckets) {
  //   cerr << x << " " << y << "\n";
  // }
  // cerr << "\n\n";

  for (int i = 1; i <= M / 2; i++) {
    if (buckets[M / 2 - i].second + buckets[M / 2 + i].second < 3 || 
      buckets[M / 2 - i].first != buckets[M / 2 + i].first) {
        cout << 0 << "\n";
        return 0;
      }
  }

  cout << buckets[M / 2].second + 1 << "\n";
  return 0;
}