#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i, n) for(int i = 0; i < (int)(n); ++i)

int solve(void) {
    string S;
    cin >> S;
    const int N = S.size();
    
    auto check = [&](string T) {
    	int b1 = (T[0] == T[1]);
    	int b2 = (T[1] == T[2]);
    	return (b1 ^ b2);
    };
    
    int cnt = 0;
    rep(i, N - 2) if(check(S.substr(i, 3))) cnt += 1;
    
    cout << cnt << "\n";
    
    return 0;
}

signed main(void) {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    
    int Testcases = 1;
    //cin >> Testcases;
    while(Testcases--) solve();
    
    return 0;
}