import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) {
	      BufferedReader stdReader =new BufferedReader(new InputStreamReader(System.in));
	      try {
	    	  String[] elements = stdReader.readLine().split(" ");
	    	  int N = Integer.parseInt(elements[0]);
	    	  int K = Integer.parseInt(elements[1])-1;
	    	  String c = stdReader.readLine();
	    	  int count = 0;
	    	  if((""+c.charAt(K)).equals("(")){
	    		  for(int i=K;i<N;i++){
	    			  if((""+c.charAt(i)).equals("(")) count++;
	    			  else count--;  
	    			  if(count == 0){
	    				  System.out.println(i+1);
	    				  break;
	    			  }
	    		  }
	    	  }else{
	    		  for(int i=K;0<=i;i--){
	    			  if((""+c.charAt(i)).equals(")"))count++;
	    			  else count--;    			  
	    			  if(count == 0){
	    				  System.out.println(i+1);
	    				  break;
	    			  }
	    		  }
	    	  }
	    	  } catch (IOException e) {
			e.printStackTrace();
	      }
	}
}