#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 mrep(i,a) for(ll i=a;i>=0;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;
	bool flag = false;
	if (s[k] == '('){
		nrep(i, k, n){
			if (s[i] == '(') count++;
			else count--;
			if (!count){
				cout << i + 1 << endl;
				break;
			}
		}
	}
	else{
		mrep(i, k){
			if (s[i] == ')') count++;
			else count--;
			if (!count){
				cout << i + 1 << endl;
				break;
			}
		}
	}
	return 0;
}