package main

import (
	"fmt"
	"strings"
)

func main() {
	var N, K int
	var S string
	fmt.Scan(&N, &K, &S)
	N -= 1
	K -= 1
	s := strings.Split(S, "")
	count := 0
	if s[K] == "(" {
		for i := K; i < len(s); i++ {
			if s[i] == "(" {
				count += 1
			} else {
				count -= 1
			}
			if count == 0 {
				fmt.Println(i + 1)
				return
			}
		}
	} else {
		for i := K; i >= 0; i-- {
			if s[i] == ")" {
				count += 1
			} else {
				count -= 1
			}
			if count == 0 {
				fmt.Println(i + 1)
				return
			}
		}
	}
}