int led1 = 13;
int led2 = 12;
int led3 = 11;
int led4 = 10;
int led5 = 9;
int led6 = 8;

void setup() {
  // put your setup code here, to run once:
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);
  pinMode(led5, OUTPUT);
  pinMode(led6, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  int leds[] = {led1, led2, led3, led4, led5, led6};
  
  for (int i = 0; i < 6; i++) {
    digitalWrite(leds[i], HIGH);
    delay(1000);
    digitalWrite(leds[i], LOW);
    delay(1000);
  }

  for (int i = 0; i < 6; i++) {
    digitalWrite(leds[i], HIGH);
  }
  delay(1000);

  for (int i = 0; i < 6; i++) {
    digitalWrite(leds[i], LOW);
  }
  delay(1000);

}