let [|n; k|] = stdin.ReadLine().Split " " |> Array.map int
let s = stdin.ReadLine ()

let mutable count = 0
let countArr =
    [|
        for i in s ->
            if i = '(' then
                let c = count
                count <- count + 1
                c
            else
                count <- count - 1
                count
    |]
    
let k_num = countArr.[k-1]
if s.[k-1] = '(' then
    for i = k to s.Length-1 do
        if countArr.[i] = k_num then
            printfn "%d" (i+1)
            exit 0
if s.[k-1] = ')' then
    for i = k-2 downto 0 do
        if countArr.[i] = k_num then
            printfn "%d" (i+1)
            exit 0