#include <iostream>
#include <string>
using namespace std;

int main()
{
    int N, K;
    string S;
    cin >> N >> K;
    cin >> S;
    int cnt;
    if (S[K - 1] == '(')
    {
        cnt = 1;
        for (int i = K; i < N; i++)
        {
            if (S[i] == '(')
            {
                cnt++;
            }
            else
            {
                cnt--;
                if (cnt == 0)
                {
                    cout << i + 1 << endl;
                    return 0;
                }
            }
        }
    }
    else
    {
        cnt = -1;
        for (int i = K - 2; i >= 0; i--)
        {
            if (S[i] == '(')
            {
                cnt++;
                if (cnt == 0)
                {
                    cout << i + 1 << endl;
                    return 0;
                }
            }
            else
            {
                cnt--;
            }
        }
    }
    return 0;
}