if __name__ == "__main__":
    nk_array = list(map(int, input().split(" ")))
    n = nk_array[0]
    k = nk_array[1]

    kakko_str = input()
    kakko_list = []
    index = 0

    for i in range(n):
        if kakko_str[i] == "(":
            index = index + 1
            kakko_list.append(index)
            pass
        else:
            kakko_list.append(index)
            index = index - 1
            pass

    if kakko_str[k - 1] == "(":
        for i in range(k, n):
            if kakko_list[k - 1] == kakko_list[i]:
                print(i + 1)
                break
    else:
        for i in range(1, k):
            if kakko_list[k - 1] == kakko_list[k - i - 1]:
                print(k - i)
                break