#include<iostream>
#include<string>
#include<vector>
#include<set>
#include<algorithm>
#include<queue>
#include<functional>
#define ll long long
#define PLL pair<ll,ll>
#define VS vector<string>
#define VL vector<ll>
#define rep(i,a) for (ll i=0;i<a;i++)
#define nrep(i,n,a) for (ll i=n;i<a;i++)
#define INF 1145141919810
#define VMIN(vec) *std::max_element(vec.begin(),vec.end())
#define VMIN(vec) *std::max_element(vec.begin(),vec.end())
#define TS(n) to_string(n)

using namespace std;


int main() {
	ll n, k;
	string s;
	cin >> n >> k >> s;
	k--;
	ll count = 0;
	ll index = 0;
	bool flag = false;
	rep(i, n){
		if (flag && s[i] == '(') count++;
		if (flag && s[i] == ')') count--;
		if (i == k){
			flag = true;
			count++;
		}if (flag && !count){
			cout << i + 1 << endl;
			break;
		}
	}
	return 0;
}