n,k=map(int,input().split())
s=input()
a=s[k-1]
ans=0
if a=="(":
  for i in range(k,n):
    if ans==0 and s[i]==")":
      print(i+1)
      break
    else:
      if s[i]=="(":
        ans+=1
      else:
        ans-=1
if a==")":
  for i in range(k-2,-1,-1):
    if ans==0 and s[i]=="(":
      print(i+1)
      break
    else:
      if s[i]=="(":
        ans-=1
      else:
        ans+=1