void setup() {
  pinMode(23, OUTPUT);
  pinMode(22, OUTPUT);
  pinMode(21, OUTPUT);
  pinMode(19, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(2, OUTPUT);
  pinMode(15, OUTPUT);
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(23, INPUT);
  digitalWrite(22, INPUT);
  digitalWrite(21, INPUT);
  digitalWrite(19, INPUT);
  delay(100);
  digitalWrite(23, LOW);
  digitalWrite(22, LOW);
  digitalWrite(21, LOW);
  digitalWrite(19, LOW);
  delay(100);
  digitalWrite(4, INPUT);
  digitalWrite(2, INPUT);
  digitalWrite(15, INPUT);
  digitalWrite(13, INPUT);
  delay(100);
  digitalWrite(4, LOW);
  digitalWrite(2, LOW);
  digitalWrite(15, LOW);
  digitalWrite(13, LOW);
  delay(100);
}