void setup() {
  // put your setup code here, to run once:
pinMode(21, OUTPUT);
pinMode(19, OUTPUT);
pinMode(18, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(21, HIGH);
  delay(500); // this  speeds up the simulation 
  digitalWrite(21, LOW);
  delay(500);
  //jeda
  digitalWrite(19, HIGH);
  delay(500);
  digitalWrite(19, LOW);
  //jeda
  digitalWrite(18, HIGH);
  delay(500);
  digitalWrite(28, LOW);

}