import sys
# input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################


s = input()
ans = 0
n = len(s)
for i in range(n - 2):
    if (s[i] == s[i+1] or s[i+1] == s[i+2]) and s[i] != s[i+2]:
        ans += 1

print(ans)