#include<bits/stdc++.h>
#include<atcoder/all>
#define chmin(x,y) (x) = min((x),(y))
#define chmax(x,y) (x) = max((x),(y))
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define vec vector
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back 
#define eb emplace_back

using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
const ll mod = 998244353;
using mint = modint998244353;
const vector<int> dx = {1,0,-1,0}, dy = {0,1,0,-1};
// using Graph = vector<vector<pair<int,ll>>>;
using Graph = vector<vector<int>>;

int main(){
  // input
  string S;
  cin >> S;
  int N = S.size();

  // solve
  int ans = 0;
  rep(i,N-2){
    int judge = 0;
    if(S[i] == S[i+1]) judge++;
    if(S[i+2] == S[i+1]) judge++;

    if(judge == 1) ans++;
  }
  
  // output
  cout << ans << endl;
}