S = input()
c = 0

for i in range(len(S)-2):
    s1 = S[i]
    s2 = S[i+1]
    s3 = S[i+2]

    if (s1 == s2 and s2 != s3) or (s1 != s2 and s2 == s3):
        c += 1

print(c)