#define _USE_MATH_DEFINES

#include <iostream>	//cin, cout
#include <vector>	//vector
#include <algorithm> //sort,min,max,count
#include <string>	//string,getline, to_string
#include <ios>		//fixed
#include <iomanip>	//setprecision
#include <utility> //swap, pair
#include <cstdlib>	//abs(int)
#include <cmath>	//sqrt,ceil,M_PI, pow, sin
#include <sstream>	//stringstream, getline
#include <numeric>	//gcd, accumlate
#include <deque>	//deque
#include <random>	//randam_device
#include <limits>	//numeric_limits

using namespace std;
constexpr long long int D_MOD = 1000000007;

int main() {

	int N, K;
	string S;
	cin >> N >> K >> S;

	int temp = 0;

	if (S[K - 1] == '(') {
		for (int i = K; i < N; i++) {
			if (S[i] == '(') {
				temp++;
			}
			else {
				if (temp != 0) {
					temp--;
				}
				else {
					cout << i + 1 << endl;
					return 0;
				}
			}
		}
	}
	else {
		for (int i = K - 2; i >= 0; i--) {
			if (S[i] == ')') {
				temp++;
			}
			else {
				if (temp != 0) {
					temp--;
				}
				else {
					cout << i + 1 << endl;
					return 0;
				}
			}
		}
	}

	return 0;

}