#include <bits/stdc++.h>
using namespace std;
string DBG_DLM(int& i) { return (i++ == 0 ? "" : ", "); }
template <class T>
ostream& operator<<(ostream& os, vector<T> v);
template <class T>
ostream& operator<<(ostream& os, set<T> v);
template <class T>
ostream& operator<<(ostream& os, queue<T> q);
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q);
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p);
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> mp);
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> mp);
template <int I, class TPL>
void DBG(ostream& os, TPL t) {}
template <int I, class TPL, class H, class... Ts>
void DBG(ostream& os, TPL t) {
  os << (I == 0 ? "" : ", ") << get<I>(t);
  DBG<I + 1, TPL, Ts...>(os, t);
}
template <class T, class K>
void DBG(ostream& os, pair<T, K> p, string delim) {
  os << "(" << p.first << delim << p.second << ")";
}
template <class... Ts>
ostream& operator<<(ostream& os, tuple<Ts...> t) {
  os << "(";
  DBG<0, tuple<Ts...>, Ts...>(os, t);
  os << ")";
  return os;
}
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p) {
  DBG(os, p, ", ");
  return os;
}
template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : v) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, set<T> s) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : s) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.front();
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.top();
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using vs = vector<string>;
using vvs = vector<vs>;
using vvvs = vector<vvs>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vvvd = vector<vvd>;
using vpii = vector<pii>;
using vvpii = vector<vpii>;
using vvvpii = vector<vvpii>;
template <class A, class B>
bool amax(A& a, const B& b) {
  return b > a ? a = b, 1 : 0;
}
template <class A, class B>
bool amin(A& a, const B& b) {
  return b < a ? a = b, 1 : 0;
}
ll ri() {
  ll l;
  cin >> l;
  return l;
}
string rs() {
  string s;
  cin >> s;
  return s;
}
ll solve() {
  auto s = rs();
  int n = ((int)(s).size());
  ;
  int ans = 0;
  char p = '-';
  vector<pair<char, pair<int, pii>>> A;
  for (int i = int(0); i < int(n); ++i) {
    char c = s[i];
    if (c != p) {
      A.emplace_back(c, make_pair(0, pii(0, 0)));
      p = c;
    }
    A.back().second.first++;
  }
  for (int i = int(0); i < int(((int)(A).size())); ++i)
    A[i].second.second.first = i - 1;
  for (int i = int(0); i < int(((int)(A).size())); ++i)
    A[i].second.second.second = i + 1;
  A.front().second.second.first = -1;
  A.back().second.second.second = -1;
  ;
  int head = 0;
  while (1) {
    ;
    if (head < 0 || A[head].second.second.second < 0) break;
    ;
    {
      int p = head;
      while (p != -1) {
        if (A[p].second.second.second != -1 &&
            A[A[p].second.second.second].first != A[p].first) {
          A[p].second.first--;
          A[A[p].second.second.second].second.first--;
        }
        p = A[p].second.second.second;
      }
    };
    while (head != -1 && A[head].second.first <= 0) {
      head = A[head].second.second.second;
    }
    {
      int p = head;
      while (p != -1) {
        while (A[p].second.second.second != -1 &&
               A[A[p].second.second.second].second.first <= 0) {
          A[p].second.second.second =
              A[A[p].second.second.second].second.second.second;
        }
        p = A[p].second.second.second;
      }
    }
    {
      int p = head;
      while (p != -1) {
        while (A[p].second.second.second != -1 &&
               A[A[p].second.second.second].first == A[p].first) {
          A[p].second.first += A[A[p].second.second.second].second.first;
          A[p].second.second.second =
              A[A[p].second.second.second].second.second.second;
        }
        p = A[p].second.second.second;
      }
    }
    ans++;
  }
  return ans;
}
void Main() { cout << solve() << endl; }
signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  Main();
  return 0;
}
