#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
using namespace std;
#define REP(i, a, n) for(int i=a; i<n; i++)
#define RREP(i, a, n) for(int i=n-1; i>=a; i--)

int main()
{
	int N, K;
	string S;
	cin >> N >> K >> S;

	if (S[K - 1] == '(') {
		int cnt = 1;
		REP(i, K, S.size()) {
			if (S[i] == '(') cnt++;
			else cnt--;

			if (cnt == 0) {
				cout << i + 1 << endl;
				break;
			}
		}
	}

	else {
		int cnt = 1;
		RREP(i, 0, K - 1) {
			if (S[i] == ')') cnt++;
			else cnt--;

			if (cnt == 0) {
				cout << i + 1 << endl;
				break;
			}
		}
	}

	return 0;
}