#include <bits/stdc++.h>
#define MOD 1000000007

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long LL;

const double EPS = 1e-8;
const int INF = 1e9;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

int main(void) {
	int N,K;
	cin >> N >> K;
	string s;
	cin >> s;
	K--;

	int cnt = 0;
	if(s[K] == '(')
	for(int i=K+1;i<s.size();i++){
		if(s[i] == ')' && cnt == 0){
			cout << i+1 << endl;
			exit(0);
		}
		if(s[i] == '(')cnt++;
		else cnt--;
	}
	
	for(int i=K+1;i>=0;i--){
		if(s[i] == '(' && cnt == 0){
			cout << i+1 << endl;
			exit(0);
		}
		if(s[i] == ')')cnt++;
		else cnt--;
	}

	return 0;
}