use proconio::{input, marker::Chars};

fn solve() -> usize {
  input! {
    s: Chars,
  }
  let mut ans = 0;
  for i in 0..s.len()-2 {
    if (s[i] == s[i+1] && s[i+1] != s[i+2]) || (s[i] != s[i+1] && s[i+1] == s[i+2]) {
      ans += 1;
    }
  }
  ans
}

fn main() {
  let ans = solve();
  println!("{}", ans);
}