void setup() {
  
pinMode(13, OUTPUT);


}

void loop() {
  
  for (int i=13; i>4; i--)

  {
digitalWrite(i, HIGH);
delay(500);
digitalWrite(i, LOW);
delay(500);
  }


  for (int j=4; j<13;j++)
  
{
  digitalWrite(j, HIGH);
  delay(500);
  digitalWrite(j, LOW);
  delay(500);
  
  }

}