n = gets.to_i
a = 3162277660168 # sqrt of 10**25
result = false
while a * 2 < n
  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
  a -= 1
end
puts result ? 1 : -1