Did you know?

  On Arduino Uno, 40*1000 != 40000

  When you multiply 40 by 1000, the compiler treats these numbers as `int` values.
  int values are 16-bit signed values, meaning they can only take values between
  -32768 and 32767. 

  When you multiply two int values, the result is also an int value. In this case,
  the result falls out of the range of int, so you get a negative number.

  If you want the compiler to treat the constants as long integers (with a 32 bit
  range, from -2,147,483,648 to 2,147,483,647), simply add the letter L after the constant.
  Try changing the first print to `40 * 1000L` and observe the result!

void setup() {
  Serial.println(40 * 1000);

void loop() {