#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<long long, long long>;
const long long INF = 2e18;
template <class A, class B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}
template <class A>
ostream &operator<<(ostream &os, const vector<A> &v) {
  os << "{";
  for (long long i = 0; i < (long long)v.size(); i++)
    if (i == 0)
      os << v[i];
    else
      os << ", " << v[i];
  os << "}";
  return os;
}
void dprint(string s) { cout << "\n"; }
template <class T, class... U>
void dprint(string s, T t, U... u) {
  long long w = s.find(',');
  cout << "[" << s.substr(0, w) << ": " << t << "] ";
  dprint(s.substr(w + 2, (long long)s.size() - w - 1), u...);
}
const long long N = 1e6 + 5;
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  vector<pair<char, long long>> v;
  for (long long i = 0; i < (long long)(s).size();) {
    char c = s[i];
    long long cnt = 0;
    while (s[i] == c and i < (long long)(s).size()) cnt++, i++;
    v.push_back({c, cnt});
  }
  if ((long long)(v).size() % 2) {
    bool ok = 1;
    for (long long i = 0; i < (long long)(v).size() / 2; i++) {
      if (v[i].first == v[(long long)(v).size() - 1 - i].first and
          v[i].second + v[(long long)(v).size() - 1 - i].second >= 3)
        ;
      else
        ok = 0;
    }
    if (v[(long long)(v).size() / 2].second == 1) ok = 0;
    if (ok)
      cout << v[(long long)(v).size() / 2].second + 1;
    else
      cout << 0;
  } else {
    cout << 0;
  }
  return 0;
}
