fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)


fun findAns n =
    let
        fun findAnsAux x =
            let
                val shorter = x div 2
                val longer = x - shorter
            in
                shorter * longer
            end

        val nn = if n mod 2 = 0 then n
                 else n - 1
    in
        if nn < 4
        then 0
        else findAnsAux (nn div 2)
    end


val () =
    let
        val d = readInt ()
                        
        val ans = findAns d
    in    
        print (Int.toString ans ^ "\n")
    end