#![allow(unused_imports, unused_macros)]
use myu2::*;
use std::cmp::*;
use std::collections::*;
use std::io::Read;

fn main() {
    input! {
        n: usize, c: chars
    }

    let mut ans = if c[0] == 'B' && c[1] == 'B' { 0 } else { 1 };
    for i in 1..n - 1 {
        if c[i] == 'A' && c[i + 1] == 'A' {
            ans += 1;
        } else if c[i] == 'A' && c[i + 1] == 'B' && c[i - 1] == 'A' {
            ans += 1;
        } else if c[i] == 'B' && c[i + 1] == 'A' {
            ans += 1;
        }
    }
    for i in 0..n - 1 {
        if c[i] == 'B' && c[i + 1] == 'B' {
            ans += 1;
            break;
        }
    }
    println!("{}", ans);
}

// lib

// util
#[macro_use]
pub mod myu2 {
    // input
    #[macro_export]
    macro_rules! input { ($($r:tt)*) => { let mut bytes = std::io::Read::bytes(std::io::BufReader::new(std::io::stdin())); let mut next = move |is_word: bool| -> String{if is_word { bytes.by_ref().map(|r|r.unwrap() as char).skip_while(|c|c.is_whitespace()).take_while(|c|!c.is_whitespace()).collect() } else { bytes.by_ref().map(|r|r.unwrap() as char).skip_while(|c| c == &'\n').take_while(|c| c != &'\n').collect() } }; input_inner!{next, $($r)*}; }; }
    #[macro_export]
    macro_rules! input_inner { ($next:expr) => {}; ($next:expr, ) => {}; ($next:expr, static $var:ident : $t:tt $($rest:tt)*) => { $var = read_value!($next, $t); input_inner!{$next $($rest)*} }; ($next:expr, mut $var:ident : $t:tt $($rest:tt)*) => { let mut $var = read_value!($next, $t); input_inner!{$next $($rest)*} }; ($next:expr, $var:ident : $t:tt $($rest:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($rest)*} }; }
    #[macro_export]
    macro_rules! read_value { ($next:expr, ( $($t:tt),* )) => { ( $(read_value!($next, $t)),* ) }; ($next:expr, [ $t:tt ; all ]) => { { let mut str = $next(false); str.split_whitespace().map(|it| it.parse::<$t>().unwrap()).collect::<Vec<_>>() } }; ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len as usize).map(|_| read_value!($next, $t)).collect::<Vec<_>>() }; ($next:expr, chars) => { read_value!($next, String).chars().collect::<Vec<char>>() }; ($next:expr, lines) => { { let mut vec = Vec::new(); let mut str = $next(false); while str != "" { vec.push(str); str = $next(false); } vec } }; ($next:expr, line) => { $next(false) }; ($next:expr, usize1) => { read_value!($next, usize) - 1 }; ($next:expr, $t:ty) => { $next(true).parse::<$t>().expect("Parse error") }; }
    // min, max
    #[macro_export]
    macro_rules! min { ($a:expr $(,)*) => {{ $a }}; ($a:expr, $b:expr $(,)*) => {{ std::cmp::min($a, $b) }}; ($a:expr, $($rest:expr),+ $(,)*) => {{ std::cmp::min($a, min!($($rest),+)) }}; }
    #[macro_export]
    macro_rules! max { ($a:expr $(,)*) => {{ $a }}; ($a:expr, $b:expr $(,)*) => {{ std::cmp::max($a, $b) }}; ($a:expr, $($rest:expr),+ $(,)*) => {{ std::cmp::max($a, max!($($rest),+)) }}; }
    // chmin, chmax
    #[macro_export]
    macro_rules! chmin { ($base:expr, $($cmps:expr),+ $(,)*) => {{ let cmp_min = min!($($cmps),+); if $base > cmp_min { $base = cmp_min; true } else { false } }}; }
    #[macro_export]
    macro_rules! chmax { ($base:expr, $($cmps:expr),+ $(,)*) => {{ let cmp_max = max!($($cmps),+); if $base < cmp_max { $base = cmp_max; true } else { false } }}; }
    // std::collections
    #[macro_export]
    macro_rules! hashmap { ($( $key: expr => $val: expr ),*) => {{ let mut map = ::std::collections::HashMap::new(); $( map.insert($key, $val); )* map } } }
}