void setup() {
  // put your setup code here, to run once:

  // Initialize digital pin LED_BUILTIN as an output
  pinMode(LED_BUILTIN, OUTPUT);  // LED_BUILTIN => 13

}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(13, HIGH); // Turn the LED on
  delay(1000);  // Wait a second
  digitalWrite(13, LOW); // Turn the LED on
  delay(1000);
}