void setup() {
  pinMode(21,OUTPUT);
  pinMode(19,OUTPUT);
  pinMode(18,OUTPUT);
  pinMode(5,OUTPUT);
}

void loop() {
  

  digitalWrite(21, HIGH);
  delay(1000);
  digitalWrite(19, HIGH);
  delay(1000);
  digitalWrite(18, HIGH);
  delay(1000);
  digitalWrite(5, HIGH);
  delay(1000);

  digitalWrite(21, LOW);
  delay(1000);
  digitalWrite(19, LOW);
  delay(1000);
  digitalWrite(18, LOW);
  delay(1000);
  digitalWrite(5, LOW);
  delay(1000);

  digitalWrite(21, HIGH);
  digitalWrite(19, LOW);
  digitalWrite(18, HIGH);
  digitalWrite(5, LOW);
  delay(1000);
  
  digitalWrite(21, LOW);
  digitalWrite(19, HIGH);
  digitalWrite(18, LOW);
  digitalWrite(5, HIGH);
  delay(1000);

  digitalWrite(21, LOW);
  digitalWrite(19, LOW);
  digitalWrite(18, LOW);
  digitalWrite(5, LOW);
  delay(1000);

}