void setup() {
  // put your setup code here, to run once:
pinMode(2, OUTPUT);
pinMode(4, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(2, HIGH);
delay(500);
digitalWrite(2,LOW);
delay(0);
digitalWrite(4, HIGH);
delay(500);
digitalWrite(4,LOW);
delay(0);
}