#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
using namespace std;
#define lint long long int
/*
vector<char>al(26);
al = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
vector<char>AL(26);
AL = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
*/

int main() {
	int N, K;
	string S;
	cin >> N >> K >> S;
	int Z = S.size();
	int cnta = 0;
	int cntb = 0;
	int I = 0;

	if (S.at(K - 1) == '(') {
		for (int i = 0; i < K; i++) {
			if (S.at(i) == '(') cnta++;
			if (S.at(i) == ')') cnta--;
		}
		for (int i = 0; i < N; i++) {
			if (S.at(Z - i - 1) == ')') cntb++;
			if (S.at(Z - i - 1) == '(') cntb--;
			if (cntb == cnta) {
				I = i;
				break;
			}
		}
		cout << Z - I << endl;
	}

	if (S.at(K - 1) == ')') {
		for (int i = 0; i < K; i++) {
			if (S.at(i) == '(') cnta++;
			if (S.at(i) == ')') cnta--;
		}
		for (int i = Z-K+1; i < N; i++) {
			if (S.at(Z - i - 1) == ')') cntb++;
			if (S.at(Z - i - 1) == '(') cntb--;
			if (cntb == cnta) {
				I = i;
				break;
			}
		}
		cout << Z - I-1 << endl;
	}
}