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


fun isCompositeNumber n =
    let
        fun isPrime i =
            let
                fun testLoop j =
                    if i < j * j then true
                    else if i mod j = 0 then false
                    else testLoop (j + 1)
            in
                testLoop 2
            end
    in
        not (isPrime n)
    end

            

        
val () =
    let
        val n = readInt ()
        
        fun findAns i =
            if isCompositeNumber i then i
            else findAns (i + 1)

        val ans = findAns (n - 100)
    in
        print (Int.toString ans ^ "\n")
    end