import java.util.Scanner
object no22{
  def main(args: Array[String]) {
    val scan = new Scanner(System.in)
    val n,k = scan.nextInt
    val s = scan.next
    var a = scala.collection.mutable.ListBuffer[(Char,Int)]()
    for(i <- Range(0,n)) s(i) match{
        case '(' => a:+=('(',i)
        case ')' => {
            if(a.last._2 == k-1){
                println(i+1)
                return
            }
            if(i == k-1){
                println(a.last._2+1)
                return
            }
        }
        a.remove(a.size-1)
    }
  }
}