void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(3, OUTPUT);
}

// the loop function runs over again forever
 void loop () {
  digitalWrite(3, HIGH);   //turn the LED on (HIGH ir the voltage level)
  delay(1000);                      //wait for a segund
  digitalWrite(3, LOW);  //turn the LED off ny making the voltage LOW
  delay(1000);                    //wait for a segund
}