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

}

void loop() {

  digitalWrite(1,HIGH);
  delay(1000);
  digitalWrite(1,LOW);
  delay(1000);  
  digitalWrite(2,HIGH);
  delay(1000);
  digitalWrite(2,LOW);
  delay(1000);  
  digitalWrite(3,HIGH);
  delay(1000);
  digitalWrite(3,LOW);
  delay(1000);  

}