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

fn main(){
    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;
        }
    }

    println!("{}", ans);
}