import java.util.*
fun main(args: Array<String>) {
    val cin = Scanner(System.`in`)
    val length :Int = Integer.parseInt(cin.next())
    val startIndex :Int = Integer.parseInt(cin.next()) -1
    val brackets :String = cin.next()
    
    val startBracket = brackets.get(startIndex)
    val direction :Int = if(startBracket.equals('(')) 1 else -1
    
    var index = startIndex
    var counter :Int = 0
    /*
    println(brackets)
    println("brackets length = " + length)
    println("start index = " + (startIndex + 1))
    println("start bracket = " + brackets.get(startIndex))
    println("direction = " + direction)
    */
    do {
        index += direction
        //println("now index = " + index)
        counter += if(brackets.get(index).equals(startBracket)) 1 else -1
        //println("counter = " + counter)
    } while(counter > -1)
    
    println (index + 1)
}