#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<stdio.h>
#include<cmath>
#include<vector>
#include<utility>
#include<stack>
#include<queue>
#include<list>
#include<bitset>
#include<functional>

#define FOR(i, a, b) for(int i=(a);i<=(b);i++)
#define RFOR(i, a, b) for(int i=(a);i>=(b);i--)
#define MOD 1000000007
#define INF 1000000000
#define PI 3.14159265358979

using namespace std;
typedef pair<int, int> P;

int main(void) {
	int n, k;
	string s;
	int dp[10001] = {};
	int p = 0;

	cin >> n >> k;
	cin >> s;

	if (s[k - 1] == '(') {
		FOR(i, k, s.size()-1) {
			if (s[i] == '(') {
				p++;
			}
			if (s[i] == ')') {
				p--;
			}
			if (p < 0) {
				cout << i+1 << endl;
				break;
			}
		}
	}
	else {
		RFOR(i, k-2, 0) {
			if (s[i] == '(') {
				p--;
			}
			if (s[i] == ')') {
				p++;
			}
			if (p < 0) {
				cout << i + 1 << endl;
				break;
			}
		}
	}

	return 0;
}