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

proc trfm(i: int): int =
  var v = A
  var arr = newSeqWith(0, 0)
  while v != 0:
    arr.insert v mod i
    v = v div i
    if arr.max > 9 or arr.len > N.repr.len: return 0
  result = arr.join("").parseInt

for i in 2 .. A:
  if i.trfm == N:
    echo i
    quit()

echo -1