#define LED_A0 A0
#define LED_A5 A5
#define LED_4  4
#define LED_3  3
#define DELAY_MS 500

void setup() {
  pinMode(LED_A0, OUTPUT); // Set A0 as an output
  pinMode(LED_A5, OUTPUT); // Set A5 as an output
  pinMode(LED_3, OUTPUT);  // Set 4 as an output
  pinMode(LED_4, OUTPUT);  // Set 3 as an output
}

void loop() {
  blink(LED_A0);
  blink(LED_A5);
  blink(LED_3);
  blink(LED_4);
}

void blink(int pin) {
  digitalWrite(pin, HIGH); // Turn on the LED
  delay(DELAY_MS);         // Wait for delay_ms milliseconds
  digitalWrite(pin, LOW);  // Turn off the LED
}