#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
#include <map>
#include <list>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
#include <iomanip>
#define INF 1050000000

using namespace std;

int main(void)
{
	int N, K;
	string S;
	int d = 0;
	
	cin >> N >> K;

	cin >> S;

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