int delayTime = 300;

void setup() {
  // put your setup code here, to run once:
 // Serial.begin(9600); 
  //Serial.println("Hello,World!");
   pinMode(LED_BUILTIN,OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
 // Serial.println("Hello,World!");
  digitalWrite(LED_BUILTIN,HIGH);
  delay(delayTime);
  digitalWrite(LED_BUILTIN,LOW);
  delay(delayTime);
}