#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<int, ll> i_ll;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N, K; cin >> N >> K;
	K--;
	string S; cin >> S;
	bool rev = false;
	if (S[K] == ')') {
		rev = true;
		K = S.length() - K - 1;
		reverse(S.begin(), S.end());
		for (int i = 0; i < S.length(); i++)
			if (S[i] == '(') S[i] = ')';
			else S[i] = '(';
	}
	int x = 1;
	for (K++; x > 0; K++)
		if (S[K] == '(') x++;
		else x--;
	cout << (rev ? S.length() - K + 1 : K) << endl;
}