#define MAX_LEDS 4

int myPins[MAX_LEDS] = {2,3,8,9};


void setup() {
  // put your setup code here, to run once:
  for (int i = 0; i<sizeof(myPins); i++){
    pinMode(myPins[i], OUTPUT);
  }
 
}
void loop() {
  // put your main code here, to run repeatedly:

for(int i = 0; i<sizeof(myPins)/sizeof(myPins[0]); i++){
    digitalWrite(myPins[i], HIGH);
    delay(500);
}
for(int i = sizeof(myPins)/sizeof(myPins[0]); i>=0; i--){
  
  digitalWrite(myPins[i], LOW);
  delay(500);
  
}


}