void setup() {
 pinMode(0, OUTPUT);
 pinMode(2, OUTPUT);
 pinMode(4, OUTPUT);
}

void loop() {
digitalWrite(0, HIGH);
delay (500);
digitalWrite(0, LOW);
delay (500);

digitalWrite(2, HIGH);
delay (500);
digitalWrite(2, LOW);
delay (500);

digitalWrite(4, HIGH);
delay (500);
digitalWrite(4, LOW);
delay (500);
}