use std::io::*;
use std::str::FromStr;
use utils::*;

pub fn main() {
    let i = stdin();
    let mut o = Vec::new();
    run(i.lock(), &mut o);
    stdout().write_all(&o).unwrap();
}

fn run<R: BufRead, W: Write>(i: R, o: &mut W) {
    let mut i = ReadEx::from(i);
    let (_, k) = i.read2::<usize, usize>();
    let s = i.read_line().as_bytes();

    writeln!(o, "{}", solve(s, k - 1) + 1).unwrap();
}
fn solve(s: &[u8], k: usize) -> usize {
    let mut d = 1;
    let mut i = k;
    loop {
        if s[k] == b'(' {
            i += 1;
        } else {
            i -= 1;
        }
        if s[i] == s[k] {
            d += 1;
        } else {
            d -= 1;
            if d == 0 {
                return i;
            }
        }
    }
}

mod utils {
    use super::*;

    pub struct ReadEx<R: BufRead> {
        r: R,
        s: String,
    }

    macro_rules! fn_read {
        {$f:ident($($v:ident: $t:ident),*)} => {
            pub fn $f<$($t: FromStr),*>(&mut self) -> ($($t),*) {
                let i = &mut self.read_line().split(' ');
                $(
                    let $v = next(i);
                )*
                ($($v),*)
            }
        };
    }

    impl<R: BufRead> ReadEx<R> {
        pub fn from(r: R) -> Self {
            ReadEx {
                r: r,
                s: String::new(),
            }
        }
        pub fn read_line(&mut self) -> &str {
            self.s.clear();
            self.r.read_line(&mut self.s).unwrap();
            self.s.trim()
        }

        fn_read! { read2(v1: T1, v2: T2) }
    }

    fn next<'a, T: FromStr, I: std::iter::Iterator<Item = &'a str>>(i: &mut I) -> T {
        i.next().unwrap().parse().ok().unwrap()
    }

}