local n, k = io.read("*n", "*n", "*l")
local str = io.read()
local s = ""
local mem = {}
for i = 1, n do
  s = string.sub(str, i, i)
  if(s == "(") then
    if(i == 1) then
      mem[i] = 1
    else
      mem[i] = mem[i - 1] + 1
    end
  else
    mem[i] = mem[i - 1] - 1
  end
end
if(string.sub(str, k, k) == "(") then
  for i = k + 1, n do
    if(string.sub(str, i, i) == ")" and mem[i] + 1 == mem[k]) then print(i); break end
  end
else
  for i = k - 1, 1, -1 do
    if(string.sub(str, i, i) == "(" and mem[i] == mem[k] + 1) then print(i); break end
  end
end