n,k=map(int,input().split())
s=list(input())
ct=1
if s[k-1]=='(':
  for i in range(k,n):
    if s[i]==')':
      ct-=1
    else:
      ct+=1
    if ct==0:
      print(i+1)
      exit()
else:
  for i in range(k-2,-1,-1):
    if s[i]=='(':
      ct-=1
    else:
      ct+=1
    if ct==0:
      print(i+1)
      exit()