void setup() {
  int a = 2;
  while (a < 7)  {
  // put your setup code here, to run once:
 pinMode(a, OUTPUT);
 a = a + 1;
  }

}

void loop() {
  // put your main code here, to run repeatedly:
 int a = 2;
  while (a < 7) {
    digitalWrite(a, HIGH);
    delay(125);
    digitalWrite(a, LOW);
    delay(250);

    a = a + 1;
  }
    a = 8;
    while (a > 1) {
    digitalWrite(a, HIGH);
    delay(125);
    digitalWrite(a, LOW);
    delay(250);

    a = a - 1;
    }
  
 }