void setup() {
  pinMode(13, OUTPUT);
  pinMode(8,OUTPUT);
  pinMode(7,OUTPUT);
  pinMode(6,OUTPUT);

}

void loop() {
  digitalWrite(8, HIGH);
  delay(500);
  digitalWrite(8,LOW);
  digitalWrite(13,HIGH);
  delay(500);
  digitalWrite(13,LOW);
  digitalWrite(7,HIGH);
  delay(500);
  digitalWrite(6,HIGH);
  digitalWrite(7,LOW);
  delay(500);
  digitalWrite(6,LOW);
}