import java.util.Scanner;

public class arc {
	public static void main(String args[]){
		
		//文字の読み込み
		Scanner sc=new Scanner(System.in);
		String line1=sc.nextLine();
		String line2=sc.nextLine();
		//文字の分割
		String[] ch1=line1.split(" ",0);//ch1[0]=the amount ch1[1]=question
		String[] ch2=line2.split("",0);//arcs
		
		int i,judge=0,count=0,answer=0;
		i=Integer.parseInt(ch1[1]);//この括弧のついの括弧の番号を求める
		int j=Integer.parseInt(ch1[0]);//括弧の総数
		i--;
		do{
			
			switch(ch2[i]){
				case "(": judge++;
				case ")": judge--;
			}
			
			if(judge==0){
				answer=i+1;
				break;
			}
			
			if(i==(j-1)){
				i=0;
			}else{
				i++;
			}
			
		}while(i<j);
		
		System.out.println(answer);
		
	}
}