#include <iostream>
#include <stack>

using namespace std;
using LL = long long;

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

    stack<char> stk1;
    stack<int> stk2;

    int ans;
    for (int i = 1; i <= N; i++) {
        if (S[i - 1] == '(') {
            stk1.push(S[i - 1]);
            stk2.push(i);
        } else {
            if (stk2.top() == K) {
                ans = i;
                break;
            } else if (i == K) {
                ans = stk2.top();
                break;
            } else {
                stk1.pop();
                stk2.pop();
            }
        }
    }

    cout << ans << endl;
}