Shifting

int L = 13;

void setup() {
  pinMode(13, OUTPUT);
  pinMode(14, OUTPUT);
  pinMode(15, OUTPUT);
  pinMode(16, OUTPUT);
  pinMode(17, OUTPUT);
}

void loop() {
  digitalWrite(L, HIGH);
  delay(1000);
  digitalWrite(L, LOW);
  delay(1000);

  L = L++;

  digitalWrite(L, HIGH);
  delay(1000);
  digitalWrite(L, LOW);
  delay(1000);

  L = L++;

  digitalWrite(L, HIGH);
  delay(1000);
  digitalWrite(L, LOW);
  delay(1000);

  L = L++;


  digitalWrite(L, HIGH);
  delay(1000);
  digitalWrite(L, LOW);
  delay(1000);

  L = L++;


  digitalWrite(L, HIGH);
  delay(1000);
  digitalWrite(L, LOW);
  delay(1000);

  L = L++;

  if ( L >= 18){
    L = 13;
  }


}