const int START_LED = 2;
const int END_LED = 8;
const int DELAY = 1 * 1000;


void setup() {
  // put your setup code here, to run once:
  for (int i = START_LED; i <= END_LED; i++) {
    pinMode(i, OUTPUT);
    digitalWrite(i, LOW);
  }

}

void loop() {
  // put your main code here, to run repeatedly:
  for (int i = START_LED; i <= END_LED; i++) {
    digitalWrite(i, HIGH);
    delay(DELAY);
  }

  for (int i = END_LED; i >= START_LED; i--) {
    digitalWrite(i, LOW);
    delay(DELAY);
  }

}