N, M = map(int, input().split())
s = input()
m = [-1] * N


def f(i):
    if m[i] != -1:
        return m[i]
    st = i
    i += 1
    while i < N and s[i] == '(':
        i = f(i)
        i += 1
    m[i] = st
    m[st] = i
    return i


for i in range(N):
    if s[i] == '(':
        f(i)

print(m[M - 1] + 1)