N,K = map(int,input().split())
S=input()

i=0


if S[K-1]=='(':
 for a in range(N):
 
  if S[K+a-1]==('('):
   i+=1

  else:
   i-=1
 
  if i<=0:
   break


 
 print(K+a)

else:
 for a in range(N):
  if S[K-a-1]==(')'):
   i+=1

  else:
   i-=1

  if i<=0:
   break
 
 print(K-a)