#![allow(
    non_snake_case,
    unused_variables,
    unused_assignments,
    unused_mut,
    unused_imports,
    unused_macros,
    dead_code
)]

// use ac_library::*;
use itertools::Itertools;
// use nalgebra::coordinates::X;
use proconio::{derive_readable, input, marker::*};
use std::{cmp::*, collections::*, fmt::*, hash::*, marker::PhantomData, ops::*, println};
// use rustc_hash::*;

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

    println!(
        "{}",
        S.windows(3)
            .filter(|x| (x[0] == x[1] || x[1] == x[2]) && x.iter().unique().count() == 2)
            .count()
    );
}