#include <iostream>
#include <sstream>
#include <math.h>
#include <stack>
#include <set>
#include <algorithm>
#include <string>
#include <queue>
#include <stack>
#include <map>
#include <cstdio>
#include <vector>
using namespace std;

#define INF (1 << 30)
#define INFLL (1LL << 60)

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