#include <iostream>
#include <ranges>
using namespace std::views;


namespace man {

}

int main() {
    std::cin.tie(nullptr) -> sync_with_stdio(false);
    std::string s;
    std::cin >> s;
    const int n = std::ssize(s);
    int ret = 0;
    for (const auto i: iota(0, n - 2)) {
        if ((s[i] == s[i + 1] && s[i] != s[i + 2]) || (s[i + 1] == s[i + 2] && s[i] != s[i + 1]) || (s[i + 2] == s[i] && s[i] != s[i + 1])) {
            ret++;
        }
    }
    std::cout << ret << '\n';
}