def main():
    n, k = [int(x) for x in input().split()]
    s = list(input())
    l = []

    for i in range(len(s)):
        if s[i] == "(":
            l.append(i + 1)
        else:
            num = l.pop()
            if i + 1 == k:
                ans = num
                break
            elif num == k:
                ans = i + 1
                break

    print(ans)


if __name__ == "__main__":
    main()