//using AtCoder;

class Program
{
    static void Main()
    {
        string S = Console.ReadLine();

        int ans = 0;
        for (int i = 0; i + 2 < S.Length; i++)
        {
            bool ok = false;
            if (S[i] == S[i + 1] && S[i + 1] != S[i + 2])
                ok = true;
            if (S[i] != S[i + 1] && S[i + 1] == S[i + 2])
                ok = true;

            if (ok)
                ans++;
        }
        Console.WriteLine(ans);
    }
}