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

int main() {
	int n, k, cnt;
	string s;
	
	cin >> n >> k >> s;
	
	if(s[k-1] == '('){
		cnt = 1;
		while(cnt){
			++k;
			if(s[k-1] == '(')++cnt;
			else --cnt;
		}
	}else{
		cnt = 1;
		while(cnt){
			--k;
			if(s[k-1] == ')')++cnt;
			else --cnt;
		}
	}
	
	cout << k << endl;
	
	return 0;
}