package main

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

var sc = bufio.NewScanner(os.Stdin)
var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func main() {
	sc.Split(bufio.ScanWords)
	_, k := nextInt(), nextInt()
	s := nextLine()
	count := 0

	if s[k-1] == '(' {
		for i := k; ; i++ {
			if s[i] == '(' {
				count++
				continue
			}
			count--
			if count == -1 {
				fmt.Println(i + 1)
				return
			}
		}

	}
	for i := k - 2; ; i-- {
		if s[i] == ')' {
			count++
			continue
		}
		count--
		if count == -1 {
			fmt.Println(i + 1)
			return
		}
	}
}

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	i, _ := strconv.Atoi(nextLine())
	return i
}

func nextInt64() int64 {
	i, _ := strconv.ParseInt(nextLine(), 10, 64)
	return i
}

func nextUint64() uint64 {
	i, _ := strconv.ParseUint(nextLine(), 10, 64)
	return i
}

func nextFloat() float64 {
	f, _ := strconv.ParseFloat(nextLine(), 64)
	return f
}

func readLine() string {
	buf := make([]byte, 0, 1000000)
	for {
		l, p, e := rdr.ReadLine()
		if e != nil {
			panic(e)
		}
		buf = append(buf, l...)
		if !p {
			break
		}
	}
	return string(buf)
}