const int ledCount = 4;
const int ledPins[ledCount] = {1,2,3,4};

void setup() 
{
  for (int i =0;i < ledCount;i++){
  pinMode(ledPins[i], OUTPUT);
}
}

void loop() 
{
  for (int i = 0;i < ledCount;i++){
  digitalWrite(ledPins[i],HIGH);
  delay(200);
  }
  for (int i = ledCount - 1;i >= 0;i--){
  digitalWrite(ledPins[i], LOW);
  delay(200);
}
}