int RIGHT_LED = 2;
int MIDDLE_LED = 3;
int LEFT_LED = 4;

void setup() {
  // put your setup code here, to run once:


  pinMode(RIGHT_LED, OUTPUT);
  pinMode(MIDDLE_LED, OUTPUT);
  pinMode(LEFT_LED, OUTPUT);


}

void loop() {
  // put your main code here, to run repeatedly:


  digitalWrite(RIGHT_LED, HIGH);
  digitalWrite(MIDDLE_LED, LOW);
  digitalWrite(LEFT_LED, LOW);
  delay(500);
  digitalWrite(RIGHT_LED, LOW);
  digitalWrite(MIDDLE_LED, HIGH);
  digitalWrite(LEFT_LED, LOW);
  delay(500);
  digitalWrite(RIGHT_LED, LOW);
  digitalWrite(MIDDLE_LED, LOW);
  digitalWrite(LEFT_LED, HIGH);
 delay(500);

}