void setup() {
  // put your setup code here, to run once:
pinMode(2, OUTPUT);
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
digitalWrite(2, 1);
digitalWrite(3, 1);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(4, 1);
digitalWrite(5, 0);
delay(500);
digitalWrite(4, 0);
digitalWrite(5, 1);
delay(500);
}