n, k = map(int, input().split())
s = list(input())
def f(k):
  count = 0
  if s[k-1] == ')':
    while True:
      if s[k-1] == ')':
        count += 1
      else:
        count -= 1
      
      if count == 0:
        return k
      k -= 1
  elif s[k-1] == '(':
    while True:
      if s[k-1] == '(':
        count += 1
      else:
        count -= 1
      
      if count == 0:
        return k
      k += 1

print(f(k))