#coding: utf-8
##yuki_22


nk=map(int,raw_input().split())
s=raw_input()

n=nk[0]
k=nk[1]
k=k-1
count=0

if s[k]=='(':
 for i in xrange(k,n):
  if s[i]=='(':
   count+=1
  elif s[i]==')':
   count-=1
  if count==0:
   rt=i
   break
elif s[k]==')':
 for i in xrange(k,-1,-1):  
  if s[i]==')':
   count+=1
  elif s[i]=='(':
   count-=1
  if count==0:
   rt=i
   break

print rt+1