def main() -> None:
    n, k = map(int, input().split())
    s = input()
    v = 0
    p = 0
    t = 1
    if s[k-1] == "(":
        v = 1
        p = k-1
    else:
        v = -1
        p = k
    p += v
    while True:
        # print(s,s[k-1],s[p], v, p, t)

        if s[p] != s[k-1] and t == 0:
            print(p)
            return None
        elif s[p] != s[k-1]:
            t -= 1
            p += v
        else:
            t += 1
            p += v


if __name__ == "__main__":
    main()