n = gets.to_i
a = Math.sqrt(n).to_i + 1
result = false
while a < 3162277660168
  val = 10**25
  b = 1
  while a > b
    val = a**2 - b**2
    result = true and break if val == n
    break if val < n
    b += 1
  end
  break if result
  break if a + b >= n
  a += 1
end
puts result ? 1 : -1