#![allow(non_snake_case, unused_imports)]

use std::collections::{BinaryHeap, HashMap, HashSet};
use proconio::{input, marker::Usize1, marker::Chars};
use itertools::Itertools;

#[allow(unused_macros)]
macro_rules! d {
    ( $( $x:expr ),* $(,)? ) => {
        eprintln!(
            concat!( $( stringify!($x), "={:?} " ),* ),
            $( $x ),*
        );
    };
}

#[allow(dead_code)]
fn yn(b: bool) -> &'static str {
    if b { "Yes" } else { "No" }
}

fn main() {
    input! {
        S: Chars,
    }

    let ans = S.iter()
        .tuple_windows()
        .filter(|(a, b, c)| {
            a != c && (a == b || b == c)
        })
        .count();

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