#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
typedef long long ll;
const int INF = 1<<30;
const ll INFLL = 1LL<<60;
const ll MOD = 998244353;
const double INFD = 1.0E10;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, -1, 0, 1};
map<int, char> dm = {{0, 'D'}, {1, 'L'}, {2, 'U'}, {3, 'R'}};
// const int dx[8] = {1, 1, 0, -1, -1, -1, 0, 1};
// const int dy[8] = {0, 1, 1, 1, 0, -1, -1, -1};
using Pair = pair<ll, ll>;
using mint = atcoder::modint998244353;
// using mint = atcoder::modint1000000007;






int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
    
    string s; cin >> s;
    int n = s.size();
    ll ans = 0;
    for (int i = 0; i < n - 2; i++){
        if (s[i] == s[i + 1] && s[i + 1] != s[i + 2]) ans++;
        if (s[i + 1] == s[i + 2] && s[i] != s[i + 1]) ans++;
    }
    
    cout << ans << endl;
    
    return 0;
}