int red=11;
int yellow=12;
int green=13;

void setup() {
  // put your setup code here, to run once:
pinMode(red, OUTPUT);
pinMode(yellow, OUTPUT);
pinMode(green, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(red, HIGH);
digitalWrite(yellow, LOW);
digitalWrite(green, LOW);
delay(1500);

digitalWrite(yellow, HIGH);
digitalWrite(red, LOW);
digitalWrite(green, LOW);
delay(1500);

digitalWrite(green, HIGH);
digitalWrite(yellow, LOW);
digitalWrite(red, LOW);
delay(1500);

digitalWrite(green, LOW);
digitalWrite(yellow, LOW);
digitalWrite(red, LOW);
delay(1500);

digitalWrite(green, HIGH);
digitalWrite(yellow, HIGH);
digitalWrite(red, HIGH);
delay(1500);
}