int red=13;
int yellow=8;
int green=2;


void setup() {
pinMode(red, OUTPUT);
pinMode(yellow , OUTPUT);
pinMode(green, OUTPUT);

}

void loop() {
digitalWrite(red, HIGH);
digitalWrite(yellow, LOW);
digitalWrite(green, LOW);
delay(500);

digitalWrite(red, LOW);
digitalWrite(yellow, HIGH);
digitalWrite(green, LOW);
delay(500);

digitalWrite(red, LOW);
digitalWrite(yellow , LOW);
digitalWrite(green, HIGH);
delay(500);


}