use std::io::{self, BufRead};

fn get_lines() -> Vec<String> {
    let stdin = io::stdin();
    let lines: Vec<String> = stdin.lock().lines().map(|l| l.unwrap()).collect();
    return lines;
}

fn main(){
    let l = get_lines();
    let x: Vec<i32> = l[0].split(' ').map(|x| x.parse::<i32>().unwrap()).collect();
    let (n, k) = (x[0], x[1]);
    let s = &l[1];
    let mut i = k;
    let mut r = 1;
    if n as f64 / 2.0 >= k as f64 {
        let mut x = s.chars();
        if x.nth((k - 1) as usize).unwrap() == '(' {
            for c in x {
                i += 1;
                r += if c == '(' { 1 } else { -1 };
                if r == 0 { println!("{}", i); return; }
            }
        } else {
            for c in s.chars().rev().skip((n - (k - 1)) as usize) {
                i -= 1;
                r += if c == ')' { 1 } else { -1 };
                if r == 0 { println!("{}", i); return; }
            }
        }
    } else {
        let mut x = s.chars().rev();
        if x.nth((n - k) as usize).unwrap() == ')' {
            for c in x {
                i -= 1;
                r += if c == ')' { 1 } else { -1 };
                if r == 0 { println!("{}", i); return; }
            }
        } else {
            for c in s.chars().skip(k as usize) {
                i += 1;
                r += if c == '(' { 1 } else { -1 };
                if r == 0 { println!("{}", i); return; }
            }
        }
    }
}