# coding:utf-8

n, k = map(int, input().split())
s = str(input())

a = 0
b = 0
c = 0

if k == len(s):
    print(1)
elif s[k-1] == '(':
    while True:
        if b - a == 1:
            print(k+c)
            break
        c += 1
        if s[k+c-1] == '(':
            a += 1 # '('を1つ増やす
        else:
            b += 1 # ')'を1つ増やす

elif s[k-1] == ')':
    while True:
        if b - a == 1:
            print(len(s[-k:-1])-c+1)
            break
        c += 1
        if s[k-c+1] == '(':
            a += 1 # ')'を1つ増やす
        else:
            b += 1 # '('を1つ増やす