package main

import "fmt"

func main () {
	// 入力
	var len, cursor int
	var brackets string

	fmt.Scan(&len, &cursor)
	fmt.Scan(&brackets)

	targetChar := brackets[cursor - 1:cursor]

	ans := cursor
	cnt := 0

	if targetChar == "(" {
		for ; ; ans++ {
			if brackets[ans - 1: ans] == "(" {
				cnt++
			} else {
				cnt--
			}
			if cnt <= 0 {
				break
			}
		}
	} else {
		for ; ; ans-- {
			if brackets[ans - 1: ans] == ")" {
				cnt++
			} else {
				cnt--
			}
			if cnt <= 0 {
				break
			}
		}
	}

	fmt.Println(ans)
}