int ledPins[] = {8, 9, 10};

void setup() {
  for (int i = 0; i < 3; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
  Serial.begin(9600);
}

void loop() {
  for (int i = 0; i < 3; i++) {
    digitalWrite(ledPins[i], HIGH);
    Serial.print("LED "); Serial.print(i + 1); Serial.println(" nyala");
    delay(500);
    digitalWrite(ledPins[i], LOW);
    Serial.print("LED "); Serial.print(i + 1); Serial.println(" mati");
    delay(500);
  }
}