import math._
import util.control.Breaks._
import scala.collection.mutable.ArrayBuffer

object Main {
  def main(args: Array[String]) = {
    val sc = new java.util.Scanner(System.in)
    val n, k = sc.nextInt
    val s = sc.next

    val xs = new ArrayBuffer[(Int, Char)] // (インデックス, 括弧文字)
    breakable {
      for (i <- 0 to s.length-1) s(i) match {
        case '(' => xs.append((i, '('))
        case ')' => {
          assert(xs.last._2 == '(')
          if (i == k-1) {
            println(xs.last._1 + 1)
            break
          }
          if (xs.last._1 == k-1) {
            println(i+1)
            break
          }
        }
        xs.remove(xs.length-1)
      }
    }
  }
}