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