fn main() {
    let mut nk = String::new();
    std::io::stdin().read_line(&mut nk).ok();
    let k: usize = nk.trim().split_whitespace().skip(1).next().unwrap().parse().unwrap();
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s: Vec<char> = s.trim().chars().collect();

    match s[k-1] {
        '(' => {
            let (_, target) = s.split_at(k);
            let mut count = 1;
            target.iter().enumerate().for_each(|pair| {
                let c = pair.1;
                if *c == ')' {
                    count -= 1;
                } else {
                    count += 1;
                }
                if count == 0 {
                    println!("{}", k + pair.0 + 1);
                    return;
                }
            })
        },
        ')' => {
            let (target, _) = s.split_at(k-1);
            let mut count = 1;
            target.iter().rev().enumerate().for_each(|pair| {
                let c = pair.1;
                if *c == ')' {
                    count += 1;
                } else {
                    count -= 1;
                }
                if count == 0 {
                    println!("{}", k - pair.0 - 1);
                    return;
                }
            })
        },
        _ => {}
    }
}