#include<iostream>
#include<string>

using namespace std;

int main()
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N, K, answer = 0;
	string S;

	cin >> N >> K >> S;

		if (S[K-1] == ')'){
			int cnt = 0;
			for (int i = K - 1; i >= 0; i--)
			{
				if (S[i] == ')') cnt++;
				else cnt--;
				if (cnt == 0){
					answer = i+1;
					break;
				}
			}
		}
		else{
			int cnt = 0;
			for (int i = K-1; i < N; i++)
			{
				if (S[i] == '(') cnt++;
				else cnt--;
				if (cnt == 0){
					answer = i+1;
					break;
				}
			}
		}

		cout << answer << endl;
}