void setup() {
pinMode(18, OUTPUT);
pinMode(17, OUTPUT);
pinMode(12, OUTPUT);
pinMode(13, OUTPUT);
}
void loop() 
{
digitalWrite(18, HIGH);
digitalWrite(17, LOW);
digitalWrite(12, LOW);
digitalWrite(13, LOW);
delay(1000);
digitalWrite(18, LOW);
digitalWrite(17, HIGH);
digitalWrite(12, LOW);
digitalWrite(13, LOW);
delay(1000);
digitalWrite(18, LOW);
digitalWrite(17, LOW);
digitalWrite(12, HIGH);
digitalWrite(13, LOW);
delay(1000);
digitalWrite(18, LOW);
digitalWrite(17, LOW);
digitalWrite(12, LOW);
digitalWrite(13, HIGH);
delay(1000);
}