void setup() {
  // put your setup code here, to run once:
  pinMode(13, OUTPUT);
}

void loop() {
  int l = 13, p = 12, u = 11;
  digitalWrite(l, HIGH);
  digitalWrite(p, LOW);
  digitalWrite(u, LOW);
  delay(1000);
  digitalWrite(l, HIGH);
  digitalWrite(p, HIGH);
  digitalWrite(u, LOW);
  delay(1000);
  digitalWrite(l, HIGH);
  digitalWrite(p, HIGH);
  digitalWrite(u, HIGH);
  delay(1000);
  digitalWrite(l, LOW);
  digitalWrite(p, LOW);
  digitalWrite(u, LOW);
  delay(1000);
}