let rec non_square n i =
  if n mod 4 = 0 then non_square (n / 4) 3
  else
    if i * i > n then n
    else
      if n mod (i * i) = 0 then non_square (n / (i * i)) i
      else non_square n (i + 2)

let () = print_int (non_square (int_of_string (read_line ())) 3)