void setup() {
  Serial.begin(9600);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  Serial.println("23.11.5654 MUHAMMAD AKHDAAN");
}

void loop() {
  // put your main code here, to run repeatedly:
  if(Serial.available()) {
    String perintah = Serial.readStringUntil('\n');
    if (perintah == "running led") {
      for (int i = 10; i >= 8; i--) {
        digitalWrite(i, HIGH);
        delay(1000);
        digitalWrite(i, LOW);
        delay(1000);
      }
    }
  }
}