void setup() {
  pinMode(1, OUTPUT);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);

}

void loop() {
  digitalWrite(1, HIGH);
  delay(20);
  digitalWrite(1, LOW);
  delay(20);
  digitalWrite(2, HIGH);
  delay(20);
  digitalWrite(2, LOW);
  delay(20);
  digitalWrite(3, HIGH);
  delay(20);
  digitalWrite(3, LOW);
  delay(20);

}