import java.util.*
fun main(args: Array<String>) {
    val map:Map<Char, Int> = mapOf('(' to 1, ')' to -1)
    
    val sc = Scanner(System.`in`)
    val l = Integer.parseInt(sc.next())
    val startIndex = Integer.parseInt(sc.next()) -1
    val b = sc.next() //括弧の文字列
    val startChar = b.get(startIndex) //開始位置の文字
    val dir = map.getOrElse(startChar, {0}) 
    
    var index = startIndex
    var count = 0
    do {
        index += dir
        count += if(b.get(index).equals(startChar)) 1 else -1
    } while(count > -1)
    
    println (index + 1)

}