import sequtils, strutils
let
  n: seq[int] = stdin.readline.split.map(parseInt)
  s: string = stdin.readline
var
  cnt: int = 1
  ans: int
if s[n[1]-1] == '(':
  for i in countup(n[1], n[0]-1):
    if s[i] == s[n[1]-1]:
      cnt.inc
    else:
      cnt.dec
    if cnt == 0:
      ans = i + 1
      break
else:
  for i in countdown(n[1]-2, 0):
    if s[i] == s[n[1]-1]:
      cnt.inc
    else:
      cnt.dec
    if cnt == 0:
      ans = i + 1
      break
echo ans