def unification(S: str) -> int:
    q = set([S])
    min_len = len(S)
    while len(q) > 0:
        t = []
        for s in q:
            min_len = len(s)
            for i, c in enumerate(s):
                if i + 1 < len(s) and c != s[i+1]:
                    t.append(s[:i] + s[i+2:])
        q = set(t)

    return len(S) - min_len


if __name__ == "__main__":
    S = input()
    answer = unification(S)
    print(answer)
