#include <algorithm>
#include <iostream>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <cmath>
#include <stack>
using namespace std;

int main() {
	stack<int> s;
	int N,K;
	cin >> N >> K;
	string kakko;
	cin >> kakko;
	bool chk;
	if (kakko[K-1] == '('){
		chk = true;
	}else{
		chk = false;
	}

	if (!chk){
		for (int i = 0; i<K-1 ;i++){
			if (kakko[i] == '('){
				s.push(i+1);
			}else{
				s.pop();
			}
		}
		cout << s.top() << endl;
		return 0;
	}else{
		for (int i = 0; i<N ;i++){
			if (kakko[i] == '('){
				s.push(i+1);
			}else{
				int a = s.top();
				if (a == K){
					cout << i+1 << endl;
					return 0;
				}
				s.pop();
			}
		}
	}
}