// the setup function runs once when you press reset or power the board


void setup() {  // initialize digital pin 4 as an output.
   pinMode(4, OUTPUT);
}


// the loop function runs over and over again forever


void loop() {
   digitalWrite(4, HIGH); // turn the LED on (HIGH is the voltage level)
   delay(500); // wait for a second
   digitalWrite(4, LOW); // turn the LED off by making the voltage LOW
   delay(250); // wait for a second
}