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


fun findAns i 0 = i - 1
  | findAns i n = 
    if i mod 7 = 0 then findAns (i + 1) (n - 1 + 6)
    else findAns (i + 1) (n - 1)


val () =
    let
        val n = readInt ()
                                 
        val ans = findAns 1 n
    in
        print ((Int.toString ans) ^ "\n")
    end