void setup() 
{
  // put your setup code here, to run once:
Serial.begin(9600);

pinMode(LED_BUILTIN, OUTPUT);
}

void loop() 
{
  // put your main code here, to run repeatedly:
digitalWrite(LED_BUILTIN, HIGH);
Serial.println("ON");
delay(1000);
digitalWrite(LED_BUILTIN,LOW);
Serial.println("OFF");
delay(1000);
}