// No.22 括弧の対応
package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	sc := bufio.NewScanner(os.Stdin)

	sc.Scan()
	ss := strings.Split(sc.Text(), " ")
	N, _ := strconv.Atoi(ss[0])
	K, _ := strconv.Atoi(ss[1])

	sc.Scan()
	S := sc.Text()

	k := K - 1
	if S[k] == '(' {
		p := 0
		for ; k < N; k++ {
			if S[k] == '(' {
				p++
			} else {
				p--
			}
			if p == 0 {
				fmt.Println(1 + k)
				return
			}
		}
	} else {
		p := 0
		for ; k >= 0; k-- {
			if S[k] == ')' {
				p++
			} else {
				p--
			}
			if p == 0 {
				fmt.Println(1 + k)
				return
			}
		}
	}
}