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

using ll = long long;

bool chmax(auto &a, auto b) { return a < b ? a = b, 1 : 0; }
bool chmin(auto &a, auto b) { return a > b ? a = b, 1 : 0; }

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    string S; cin >> S;
    int N = S.size();
    int ans = 0;
    for (int i = 1; i < N; ++i) {
        if (S[i] == S[i - 1]) {
            if (i - 2 >= 0 && S[i - 2] != S[i]) ++ans;
            if (i + 1 < N && S[i + 1] != S[i]) ++ans;
        }
    }
    cout << ans << '\n';
}