import strutils, sequtils
const N = 17
let A = stdin.readLine.parseInt

for i in 2 .. A:
  var
    res = 0
    v = A
    arr = newSeqWith(0, 0)
  while v != 0:
    arr.insert v mod i
    v = v div i

  if arr.len > N.repr.len:
    continue
  elif arr.max < 10:
    res = arr.join("").parseInt
    if res == N:
      echo i
      quit()

echo -1