#include <bits/stdc++.h>
// #include <atcoder/dsu>
// #include<atcoder/modint>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define YES cout<< "Yes"<< endl
#define NO cout<< "No"<< endl
#define Rep(i,s,n) for(int i = (int)(s); i < (int)(n); i++)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
template<class T, class U> bool chmax(T& x, const U& y){
    if (x < y) { x = y; return true; }
    return false;
}
template<class T, class U> bool chmin(T& x, const U& y){
    if (y < x) { x = y; return true; }
    return false;
}
#define UNIQUE(a) a.erase(unique(a.begin(),a.end()),a.end())
using namespace std;
// using mint = atcoder::modint998244353;
// using mint2 = atcoder::modint1000000007;
// using namespace atcoder;
using ll = long long;
using V = vector<ll>;
using P = pair<ll,ll>;
using i128 = __int128;

void solve(){
    string s; cin >> s;
    int ans = 0;
    rep(i,s.size()-2){
        if(s[i] == s[i+1] && s[i+1] != s[i+2]) ans++;
        else if(s[i] != s[i+1] && s[i+1] == s[i+2])ans++;
    }
    cout << ans << endl;
}
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t; 
    t = 1;
    //cin >> t;
    rep(i,t) solve();
}