void setup() {

  for (int x=6;x <=13; x++) {
    pinMode(x, OUTPUT);
  }

}


void loop() {

  for (int i=6;i <=13; i++) {
    digitalWrite(i, HIGH);
    delay(200);
    digitalWrite(i, LOW);
    delay(200);
  }
  for (int i=13;i >=6; i--) {
    digitalWrite(i, HIGH);
    delay(200);
    digitalWrite(i, LOW);
    delay(200);

  }

}