/*
yukicoder No.22
作成者：ヒロソフ
使用言語：C/C++
*/
#include <iostream>
#include <iomanip>
#include <stack>
#include <cstdio>
#include <cstring>
using namespace std;
 
int main(void) {
	int N, K;
	char *lpString;
	cin >> N >> K;
	K--;
	lpString = new char[N + 1];
 
	cin >> setw(N + 1) >> lpString;
 
	if (*(lpString + K) == '(') {
		//K番目が(の場合
 
		int level = 0;
		int targetlevel;
		for (int i = 0; i < N; i++) {
			if (*(lpString + i) == '(') {
				level++;
				if (i == K) {
					targetlevel = level;
				}
			} else if (*(lpString + i) == ')') {
				if (level == targetlevel) {
					printf("%d\n", i + 1);
					break;
				}
				level--;
			}
		}
	} else {
		//K番目が)の場合
		stack<int> PosStack;
 
		for (int i = 0; i < K  ; i++) {
			if (*(lpString + i) == '(') PosStack.push(i);
			else if (*(lpString + i) == ')') PosStack.pop();
		}
		printf("%d\n", PosStack.top() + 1);
	}
 
 
	delete[]lpString;
	return 0;
}