#include <iostream>
#include <string>
using namespace std;

int main(int argc, char** argv)
{
	int n, k, kk;
	string s;
	cin >> n >> k >> s;
	kk = k-1;

	int cnt = 0;
	if (s[kk]=='(') {
		int st = kk+1;
		string sss = s.substr(st, (s.size()-kk));
		for (int ii=0; ii<sss.size(); ++ii) {
			if (sss[ii]=='(') {
				++ cnt;
			}
			else if (cnt!=0) {
				-- cnt;
			}
			else {
				cout << (st+ii+1) << endl;
				return 0;
			}
		}
	}
	else {
		string sss = s.substr(0, kk);
		for (int ii=sss.size()-1; ii>=0; --ii) {
			if (sss[ii]==')') {
				++ cnt;
			}
			else if (cnt!=0) {
				-- cnt;
			}
			else {
				cout << (ii+1) << endl;
				return 0;
			}
		}
	}
	return 0;
}