void setup() {
  // put your setup code here, to run once:
  DDRD = DDRD | B11110000;
  DDRB = DDRB | B00001111;
}

void loop() {
  // put your main code here, to run repeatedly:
  PORTD = B11110000;
  delay(500);
  PORTB = B00001111;
  PORTD = B00000000;
  delay(500);
  PORTB = B00000000;
}