program main
  implicit none
  integer::N,K,i,depth=0,res
  integer,parameter::maxlength=10000
  character(len=maxlength)::S
  character,parameter::l='(',r=')'
  read *, N, K, S
  if (S(K:K).eq.l) then
     do i=K, LEN_TRIM(S), 1
        if(S(i:i).eq.l) then
           depth = depth + 1
        else
           depth = depth - 1
        end if
        if (depth.eq.0) then
           res = i
           exit
        end if
     end do
  else
     do i=K, 1, -1
        if(S(i:i).eq.l) then
           depth = depth + 1
        else
           depth = depth - 1
        end if
        if (depth.eq.0) then
           res = i
           exit
        end if
     end do
  end if
  print '(i0)', res

end program main