def main():
    N, K = [int(_) for _ in input().split()]
    K -= 1

    S = input()

    depth_list = []
    depth = 0
    for letter in S:
        if letter == "(":
            depth += 1
            depth_list.append(depth)
        else:
            depth_list.append(depth)
            depth -= 1

    if S[K] == "(":
        i = K+1
        while True:
            if depth_list[K] == depth_list[i]:
                print(i+1)
                return
            i += 1
    else:
        i = K-1
        while True:
            if depth_list[K] == depth_list[i]:
                print(i+1)
                return
            i -= 1

main()