import strutils, sequtils, algorithm, future, sets
proc readint(f: File): int = f.readline.parseInt
proc readints(f: File): seq[int] = f.readline.split.map(parseInt)

var
  nk = stdin.readints
  n = nk[0]
  k = nk[1] - 1
  s = stdin.readline
  m = newSeq[int](s.len)
  c = 0

for i in 0..s.high:
  m[i] = c
  if s[i] == '(':
    c += 1
  else:
    c -= 1

if s[k] == '(':
  for i in countup(k+1,s.high):
    if m[k] == m[i]:
      echo i
      break
else:
  for i in countdown(k-1,0):
    if m[k] == m[i]:
      echo i
      break