// LED changing pattern: A


const int LED_PINS[] = {5,18,19,21} ;
const int NUM_LEDS = sizeof(LED_PINS)/sizeof(int) ; 

#define OFF (LOW) 
#define ON (HIGH)

void setup() { 
  for (int i=0 ; i < NUM_LEDS ; i++) {
    pinMode(LED_PINS[i], OUTPUT);
    digitalWrite(LED_PINS[i] , (i==0) ? ON:OFF);
  }
}

void loop() {
  for(int i=0 ; i < NUM_LEDS ; i++) {
    digitalWrite(LED_PINS[i], ON);
    delay(1500);
    digitalWrite(LED_PINS[i],OFF);

  }
}