n, k = map(int, input().split())
s = input()
stk = []

for i, c in enumerate(s):
    i += 1
    if i == k:
        if c == ")":
            print(stk[-1])
            break
        else:
            stk.append("*")
    if c == "(":
        stk.append(i)
    else:
        if stk.pop() == "*":
            print(i - 1)
            break